Python 数据类型及其方法详解
Python 数据类型及其方法详解
我们在学习编程语言的时候，都会遇到数据类型，这种看着很基础也不显眼的东西，却是很重要，本文介绍了 python 的数据类型，并就每种数据类型的方法作出了详细的描述，可供知识回顾。
一、整型和长整型
整型：数据是不包含小数部分的数值型数据，比如我们所说的 1、2、3、4、122，其 type 为 "int"
长整型：也是一种数字型数据，但是一般数字很大，其 type 为 "long"
在 python2 中区分整型和长整型，在 32 位的机器上，取值范围是 - 2147483648~2147483647, 超出范围的为长整型，在 64 位的机器上，取值范围为 - 9223372036854775808～9223372036854775807（通常也与 python 的解释器的位数有关）。
在 python3 中，不存在整型和长整型之分，只有整型。
举个例子：
python2中 number = 123 print (type(number)) number2 = 2147483647 print (type(number2)) number2 = 2147483648 #我们会看到超过2147483647这个范围，在py2中整形就会变成长整形了 print (type(number2)) #运行结果 <type 'int'> <type 'int'> <type 'long'> #python3中 number = 123 print (type(number)) number2 = 2147483648 print (type(number2)) #在python3中并不会 #运行结果 <class 'int'> <class 'int'>
常用的 method 的如下：
.bit_length()
取最短 bit 位数
def bit_length(self): # real signature unknown; restored from __doc__
"""
int.bit_length() -> int
Number of bits necessary to represent self in binary.
>>> bin(37)
'0b100101'
>>> (37).bit_length()
6
"""
return 0
举个例子：
number = 12 #1100 print(number.bit_length()) #运行结果 4
二、浮点型
浮点型可以看成就是小数，type 为 float。
#浮点型 number = 1.1 print(type(number)) #运行结果 <class 'float'>
常用 method 的如下：
.as_integer_ratio()
返回元组 (X,Y)，number = k ,number.as_integer_ratio() ==>（x,y） x/y=k
def as_integer_ratio(self): # real signature unknown; restored from __doc__
"""
float.as_integer_ratio() -> (int, int)
Return a pair of integers, whose ratio is exactly equal to the original
float and with a positive denominator.
Raise OverflowError on infinities and a ValueError on NaNs.
>>> (10.0).as_integer_ratio()
(10, 1)
>>> (0.0).as_integer_ratio()
(0, 1)
>>> (-.25).as_integer_ratio()
(-1, 4)
"""
pass
举个例子
number = 0.25 print(number.as_integer_ratio()) #运行结果 (1, 4)
.hex()
以十六进制表示浮点数
def hex(self): # real signature unknown; restored from __doc__
"""
float.hex() -> string
Return a hexadecimal representation of a floating-point number.
>>> (-0.1).hex()
'-0x1.999999999999ap-4'
>>> 3.14159.hex()
'0x1.921f9f01b866ep+1'
"""
return ""
举个例子
number = 3.1415 print(number.hex()) #运行结果 0x1.921cac083126fp+1
.fromhex（）
将十六进制小数以字符串输入，返回十进制小数
def fromhex(string): # real signature unknown; restored from __doc__
"""
float.fromhex(string) -> float
Create a floating-point number from a hexadecimal string.
>>> float.fromhex('0x1.ffffp10')
2047.984375
>>> float.fromhex('-0x1p-1074')
-5e-324
"""
举个例子
print(float.fromhex('0x1.921cac083126fp+1'))
#运行结果
3.1415
.is_integer()
判断小数是不是整数，比如 3.0 为一个整数，而 3.1 不是，返回布尔值
def is_integer(self, *args, **kwargs): # real signature unknown
""" Return True if the float is an integer. """
pass
举个例子
number = 3.1415 number2 = 3.0 print(number.is_integer()) print(number2.is_integer()) #运行结果 False True
三、字符类型
字符串就是一些列的字符，在 Python 中用单引号或者双引号括起来，多行可以用三引号。
name = 'my name is Frank'
name1 = "my name is Frank"
name2 = '''my name is Frank
I'm 23 years old,
'''
print(name)
print(name1)
print(name2)
#运行结果
my name is Frank
my name is Frank
my name is Frank
I'm 23 years old
常用 method 的如下：
.capitalize()
字符串首字符大写
def capitalize(self): # real signature unknown; restored from __doc__
"""
S.capitalize() -> str
Return a capitalized version of S, i.e. make the first character
have upper case and the rest lower case.
"""
return ""
举个例子
name = 'my name is Frank' #运行结果 My name is frank
.center()
字符居中，指定宽度和填充字符（默认为空格）
def center(self, width, fillchar=None): # real signature unknown; restored from __doc__
"""
S.center(width[, fillchar]) -> str
Return S centered in a string of length width. Padding is
done using the specified fill character (default is a space)
"""
return ""
举个例子
flag = "Welcome Frank" print(flag.center(50,'*')) #运行结果 ******************Welcome Frank*******************
.count()
计算字符串中某个字符的个数，可以指定索引范围
def count(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.count(sub[, start[, end]]) -> int
Return the number of non-overlapping occurrences of substring sub in
string S[start:end]. Optional arguments start and end are
interpreted as in slice notation.
"""
return 0
举个例子
flag = 'aaababbcccaddadaddd'
print(flag.count('a'))
print(flag.count('a',0,3))
#运行结果
7
3
.encode()
编码，在 python3 中，str 默认是 unicode 数据类型，可以将其编码成 bytes 数据
def encode(self, encoding='utf-8', errors='strict'): # real signature unknown; restored from __doc__
"""
S.encode(encoding='utf-8', errors='strict') -> bytes
Encode S using the codec registered for encoding. Default encoding
is 'utf-8'. errors may be given to set a different error
handling scheme. Default is 'strict' meaning that encoding errors raise
a UnicodeEncodeError. Other possible values are 'ignore', 'replace' and
'xmlcharrefreplace' as well as any other name registered with
codecs.register_error that can handle UnicodeEncodeErrors.
"""
return b""
举个例子
flag = 'aaababbcccaddadaddd'
print(flag.encode('utf8'))
#运行结果
b'aaababbcccaddadaddd'
.endswith()
判断字符串结尾是否是某个字符串和字符，可以通过索引指定范围
def endswith(self, suffix, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.endswith(suffix[, start[, end]]) -> bool
Return True if S ends with the specified suffix, False otherwise.
With optional start, test S beginning at that position.
With optional end, stop comparing S at that position.
suffix can also be a tuple of strings to try.
"""
return False
举个例子
flag = 'aaababbcccaddadaddd'
print(flag.endswith('aa'))
print(flag.endswith('ddd'))
print(flag.endswith('dddd'))
print(flag.endswith('aaa',0,3))
print(flag.endswith('aaa',0,2))
#运行结果
False
True
False
True
False
.expandtabs()
把制表符 tab(" ") 转换为空格
def expandtabs(self, tabsize=8): # real signature unknown; restored from __doc__
"""
S.expandtabs(tabsize=8) -> str
Return a copy of S where all tab characters are expanded using spaces.
If tabsize is not given, a tab size of 8 characters is assumed.
"""
return ""
举个例子
flag = " hello python!"
print(flag)
print(flag.expandtabs()) #默认tabsize=8
print(flag.expandtabs(20))
#运行结果
hello python! #一个tab，长度为4个空格
hello python! #8个空格
hello python! #20个空格
.find()
查找字符，返回索引值，可以通过指定索引范围内查找，查找不到返回 - 1
def find(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.find(sub[, start[, end]]) -> int
Return the lowest index in S where substring sub is found,
such that sub is contained within S[start:end]. Optional
arguments start and end are interpreted as in slice notation.
Return -1 on failure.
"""
return 0
举个例子
flag = "hello python!"
print(flag.find('e'))
print(flag.find('a'))
print(flag.find('h',4,-1))
#运行结果
1
-1
9
.format()
格式化输出，使用 "{}" 符号作为操作符。
def format(self, *args, **kwargs): # known special case of str.format
"""
S.format(*args, **kwargs) -> str
Return a formatted version of S, using substitutions from args and kwargs.
The substitutions are identified by braces ('{' and '}').
"""
pass
举个例子
#位置参数
flag = "hello {0} and {1}!"
print(flag.format('python','php'))
flag = "hello {} and {}!"
print(flag.format('python','php'))
#变量参数
flag = "{name} is {age} years old!"
print(flag.format(name='Frank',age = 23))
#结合列表
infor=["Frank",23]
print("{0[0]} is {0[1]} years old".format(infor))
#运行结果
hello python and php!
hello python and php!
Frank is 23 years old!
Frank is 23 years old
.format_map()
格式化输出
def format_map(self, mapping): # real signature unknown; restored from __doc__
"""
S.format_map(mapping) -> str
Return a formatted version of S, using substitutions from mapping.
The substitutions are identified by braces ('{' and '}').
"""
return ""
举个例子
people={
'name':['Frank','Caroline'],
'age':['23','22'],
}
print("My name is {name[0]},i am {age[1]} years old !".format_map(people))
#运行结果
My name is Frank,i am 22 years old !
.index()
根据字符查找索引值，可以指定索引范围查找，查找不到会报错
def index(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.index(sub[, start[, end]]) -> int
Like S.find() but raise ValueError when the substring is not found.
"""
return 0
举个例子
flag = "hello python!"
print(flag.index("e"))
print(flag.index("o",6,-1))
#运行结果
1
10
.isalnum()
判断是否是字母或数字组合，返回布尔值
def isalnum(self): # real signature unknown; restored from __doc__
"""
S.isalnum() -> bool
Return True if all characters in S are alphanumeric
and there is at least one character in S, False otherwise.
"""
return False
举个例子
flag = "hellopython" flag1 = "hellopython22" flag2 = "hellopython!!" flag3 = "!@#!#@!!@" print(flag.isalnum()) print(flag1.isalnum()) print(flag2.isalnum()) print(flag3.isalnum()) #运行结果 True True False False
.isalpha()
判断是否是字母组合，返回布尔值
def isalpha(self): # real signature unknown; restored from __doc__
"""
S.isalpha() -> bool
Return True if all characters in S are alphabetic
and there is at least one character in S, False otherwise.
"""
return False
举个例子
flag = "hellopython" flag1 = "hellopython22" print(flag.isalpha()) print(flag1.isalpha()) #运行结果 True False
.isdecimal()
判断是否是一个十进制正整数，返回布尔值
def isdecimal(self): # real signature unknown; restored from __doc__
"""
S.isdecimal() -> bool
Return True if there are only decimal characters in S,
False otherwise.
"""
return False
举个例子
number = "1.2" number1 = "12" number2 = "-12" number3 = "1222" print(number.isdecimal()) print(number1.isdecimal()) print(number2.isdecimal()) print(number3.isdecimal()) #运行结果 False True False True
isdigit()
判断是否是一个正整数，返回布尔值，与上面 isdecimal 类似
def isdigit(self): # real signature unknown; restored from __doc__
"""
S.isdigit() -> bool
Return True if all characters in S are digits
and there is at least one character in S, False otherwise.
"""
return False
举个例子
number = "1.2" number1 = "12" number2 = "-12" number3 = "11" print(number.isdigit()) print(number1.isdigit()) print(number2.isdigit()) print(number3.isdigit()) #运行结果 False True False True
.isidentifier()
判断是否为 python 中的标识符
def isidentifier(self): # real signature unknown; restored from __doc__
"""
S.isidentifier() -> bool
Return True if S is a valid identifier according
to the language definition.
Use keyword.iskeyword() to test for reserved identifiers
such as "def" and "class".
"""
return False
举个例子
flag = "cisco" flag1 = "1cisco" flag2 = "print" print(flag.isidentifier()) print(flag1.isidentifier()) print(flag2.isidentifier()) #运行结果 True False True
.islower()
判断字符串中的字母是不是都是小写，返回布尔值
def islower(self): # real signature unknown; restored from __doc__
"""
S.islower() -> bool
Return True if all cased characters in S are lowercase and there is
at least one cased character in S, False otherwise.
"""
return False
举个例子
flag = "cisco" flag1 = "cisco222" flag2 = "Cisco" print(flag.islower()) print(flag1.islower()) print(flag2.islower()) #运行结果 True True False
.isnumeric()
判断是否为数字，这个很强大，中文字符，繁体字数字都可以识别
def isnumeric(self): # real signature unknown; restored from __doc__
"""
S.isnumeric() -> bool
Return True if there are only numeric characters in S,
False otherwise.
"""
return False
举个例子
number = "123" number1 = "一" number2 = "壹" number3 = "123q" number4 = "1.1" print(number.isnumeric()) print(number1.isnumeric()) print(number2.isnumeric()) print(number3.isnumeric()) print(number4.isnumeric()) #运行结果 True True True False False
.isprintable()
判断引号里面的是否都是可打印的，返回布尔值
def isprintable(self): # real signature unknown; restored from __doc__
"""
S.isprintable() -> bool
Return True if all characters in S are considered
printable in repr() or S is empty, False otherwise.
"""
return False
举个例子
flag = " 123" flag1 = " " flag2 = "123" flag3 = r" 123" # r 可以是转义字符失效 print(flag.isprintable()) # 不可打印 print(flag1.isprintable()) # 不可打印 print(flag2.isprintable()) print(flag3.isprintable()) #运行结果 False False True True
.isspace()
判断字符串里面都是空白位，空格或者 tab，返回布尔值
def isspace(self): # real signature unknown; restored from __doc__
"""
S.isspace() -> bool
Return True if all characters in S are whitespace
and there is at least one character in S, False otherwise.
"""
return False
举个例子
flag = ' ' #4个空格 flag1 = ' '#2个tab print(flag.isspace()) print(flag1.isspace()) #运行结果 True True
.istitle()
判断字符串里面的字符是否都是大写开头，返回布尔值
def isspace(self): # real signature unknown; restored from __doc__
"""
S.isspace() -> bool
Return True if all characters in S are whitespace
and there is at least one character in S, False otherwise.
"""
return False
举个例子
flag = "Welcome Frank" flag1 = "Welcome frank" print(flag.istitle()) print(flag1.istitle()) #运行结果 True False
.isupper()
判断是否都是字符串里的字母都是大写
def isupper(self): # real signature unknown; restored from __doc__
"""
S.isupper() -> bool
Return True if all cased characters in S are uppercase and there is
at least one cased character in S, False otherwise.
"""
return False
举个例子
flag = "WELCOME1" flag1 = "Welcome1" print(flag.isupper()) print(flag1.isupper()) #运行结果 True False
.join()
将字符串以指定的字符连接生成一个新的字符串
def join(self, iterable): # real signature unknown; restored from __doc__
"""
S.join(iterable) -> str
Return a string which is the concatenation of the strings in the
iterable. The separator between elements is S.
"""
return ""
举个例子
flag = "welcome"
print("#".join(flag))
#运行结果
w#e#l#c#o#m#e
.ljust()
左对齐，可指定字符宽度和填充字符
def ljust(self, width, fillchar=None): # real signature unknown; restored from __doc__
"""
S.ljust(width[, fillchar]) -> str
Return S left-justified in a Unicode string of length width. Padding is
done using the specified fill character (default is a space).
"""
return ""
举个例子
flag = "welcome" print(flag.ljust(20,"*")) #运行结果 welcome*************
.rjust()
右对齐，可指定字符宽度和填充字符
def rjust(self, width, fillchar=None): # real signature unknown; restored from __doc__
"""
S.rjust(width[, fillchar]) -> str
Return S right-justified in a string of length width. Padding is
done using the specified fill character (default is a space).
"""
return ""
举个例子
flag = "welcome" print(flag.rjust(20,"*")) #运行结果 *************welcome
.lower()
对字符串里的所有字母转小写
def lower(self): # real signature unknown; restored from __doc__
"""
S.lower() -> str
Return a copy of the string S converted to lowercase.
"""
return ""
举个例子
flag = "WELcome" #运行结果 welcome
.upper()
对字符串里的所有字母转大写
def upper(self): # real signature unknown; restored from __doc__
"""
S.upper() -> str
Return a copy of S converted to uppercase.
"""
return ""
举个例子
flag = "WELcome" print(flag.upper()) #运行结果 WELCOME
.title()
对字符串里的单词进行首字母大写转换
def title(self): # real signature unknown; restored from __doc__
"""
S.title() -> str
Return a titlecased version of S, i.e. words start with title case
characters, all remaining cased characters have lower case.
"""
return ""
举个例子
flag = "welcome frank" print(flag.title()) #运行结果 Welcome Frank
.lstrip()
默认去除左边空白字符，可指定去除的字符，去除指定的字符后，会被空白占位。
def lstrip(self, chars=None): # real signature unknown; restored from __doc__
"""
S.lstrip([chars]) -> str
Return a copy of the string S with leading whitespace removed.
If chars is given and not None, remove characters in chars instead.
"""
return ""
举个例子
flag = " welcome frank"
flag1 = "@@@@welcome frank"
print(flag.lstrip())
print(flag.lstrip("@"))
print(flag.lstrip("@").lstrip())
#运行结果
welcome frank
welcome frank
welcome frank
.rstrip()
默认去除右边空白字符，可指定去除的字符，去除指定的字符后，会被空白占位。
def rstrip(self, chars=None): # real signature unknown; restored from __doc__
"""
S.rstrip([chars]) -> str
Return a copy of the string S with trailing whitespace removed.
If chars is given and not None, remove characters in chars instead.
"""
return ""
举个例子
flag = "welcome frank "
flag1 = "welcome frank@@@@"
# print(flag.title())
print(flag.rstrip())
print(flag.rstrip("@"))
print(flag.rstrip("@").rstrip())
#运行结果
welcome frank
welcome frank #右边有4个空格
welcome frank
.strip()
默认去除两边空白字符，可指定去除的字符，去除指定的字符后，会被空白占位。
def strip(self, chars=None): # real signature unknown; restored from __doc__
"""
S.strip([chars]) -> str
Return a copy of the string S with leading and trailing
whitespace removed.
If chars is given and not None, remove characters in chars instead.
"""
return ""
举个例子
flag = " welcome frank "
flag1 = "@@@@welcome frank@@@@"
# print(flag.title())
print(flag.strip())
print(flag.strip("@"))
print(flag.strip("@").strip())
#运行结果
welcome frank
welcome frank #右边有4个空格
welcome frank
.maketrans() 和 translate()
创建字符映射的转换表，对于接受两个参数的最简单的调用方式，第一个参数是字符串，表示需要转换的字符，第二个参数也是字符串表示转换的目标。两个字符串的长度必须相同，为一一对应的关系。
def maketrans(self, *args, **kwargs): # real signature unknown
"""
Return a translation table usable for str.translate().
If there is only one argument, it must be a dictionary mapping Unicode
ordinals (integers) or characters to Unicode ordinals, strings or None.
Character keys will be then converted to ordinals.
If there are two arguments, they must be strings of equal length, and
in the resulting dictionary, each character in x will be mapped to the
character at the same position in y. If there is a third argument, it
must be a string, whose characters will be mapped to None in the result.
"""
pass
def translate(self, table): # real signature unknown; restored from __doc__
"""
S.translate(table) -> str
Return a copy of the string S in which each character has been mapped
through the given translation table. The table must implement
lookup/indexing via __getitem__, for instance a dictionary or list,
mapping Unicode ordinals to Unicode ordinals, strings, or None. If
this operation raises LookupError, the character is left untouched.
Characters mapped to None are deleted.
"""
return ""
举个例子
intab = "aeiou" outtab = "12345" trantab = str.maketrans(intab, outtab) str = "this is string example....wow!!!" print (str.translate(trantab)) #运行结果 th3s 3s str3ng 2x1mpl2....w4w!!!
.partition()
以指定字符分割，返回一个元组
def partition(self, sep): # real signature unknown; restored from __doc__
"""
S.partition(sep) -> (head, sep, tail)
Search for the separator sep in S, and return the part before it,
the separator itself, and the part after it. If the separator is not
found, return S and two empty strings.
"""
pass
举个例子
flag = "welcome"
print(flag.partition("e"))
#运行结果
('w', 'e', 'lcome')
.replace(）
将指定的字符替换为新的字符，可指定替换的个数
def replace(self, old, new, count=None): # real signature unknown; restored from __doc__
"""
S.replace(old, new[, count]) -> str
Return a copy of S with all occurrences of substring
old replaced by new. If the optional argument count is
given, only the first count occurrences are replaced.
"""
return ""
举个例子
flag = "welcome frank ,e.."
print(flag.replace("e","z"))
print(flag.replace("e","z",1))
#运行结果
wzlcomz frank ,z..
wzlcome frank ,e..
.rfind()
返回字符串第一次出现的位置，从右向左差，返回索引值，若没有，则返回 - 1，可根据索引范围查找
def rfind(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.rfind(sub[, start[, end]]) -> int
Return the highest index in S where substring sub is found,
such that sub is contained within S[start:end]. Optional
arguments start and end are interpreted as in slice notation.
Return -1 on failure.
"""
return 0
举个例子
flag = "welcome frank ,e.."
print(flag.rfind("e"))
print(flag.rfind("x"))
print(flag.rfind("e",0,3))
#运行结果
15
-1
1
.rindex()
查找字符索引值，从右向左，返回索引值，与 rfind 类似，查找不到会报错
def rindex(self, sub, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.rindex(sub[, start[, end]]) -> int
Like S.rfind() but raise ValueError when the substring is not found.
"""
return 0
举个例子
flag = "welcome frank ,e.."
print(flag.rindex("e"))
print(flag.rindex("e",0,3))
#运行结果
15
1
.rpartition()
以指定字符从右向左分割，只分割一次，返回元组，若没有指定的字符，则在返回的元组前面加两个空字符串
def rpartition(self, sep): # real signature unknown; restored from __doc__
"""
S.rpartition(sep) -> (head, sep, tail)
Search for the separator sep in S, starting at the end of S, and return
the part before it, the separator itself, and the part after it. If the
separator is not found, return two empty strings and S.
"""
pass
举个例子
flag = "welcome frank ,e.."
print(flag.rpartition("e"))
print(flag.rpartition("x"))
#运行结果
('welcome frank ,', 'e', '..')
('', '', 'welcome frank ,e..')
.split()
分割，可以以指定的字符分割，可指定分割的次数，默认从左向右分割，与 partition 不同的是，split 分割后会删除指定的字符，默认以空格为分割符，返回元组。
def split(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__
"""
S.split(sep=None, maxsplit=-1) -> list of strings
Return a list of the words in S, using sep as the
delimiter string. If maxsplit is given, at most maxsplit
splits are done. If sep is not specified or is None, any
whitespace string is a separator and empty strings are
removed from the result.
"""
return []
举个例子
flag = "welcome frank, e.."
print(flag.split())
print(flag.split('e'))
print(flag.split('e',1))
#运行结果
['welcome', 'frank,', 'e..']
['w', 'lcom', ' frank, ', '..']
['w', 'lcome frank, e..']
.rsplit()
与 split 类似，只是它是从右向左分
def rsplit(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__
"""
S.rsplit(sep=None, maxsplit=-1) -> list of strings
Return a list of the words in S, using sep as the
delimiter string, starting at the end of the string and
working to the front. If maxsplit is given, at most maxsplit
splits are done. If sep is not specified, any whitespace string
is a separator.
"""
return []
举个例子
flag = "welcome frank, e.."
print(flag.rsplit())
print(flag.rsplit('e'))
print(flag.rsplit('e',1))
#运行结果
['welcome', 'frank,', 'e..']
['w', 'lcom', ' frank, ', '..']
['welcome frank, ', '..']
.splitlines()
字符串转换为列表
def splitlines(self, keepends=None): # real signature unknown; restored from __doc__
"""
S.splitlines([keepends]) -> list of strings
Return a list of the lines in S, breaking at line boundaries.
Line breaks are not included in the resulting list unless keepends
is given and true.
"""
return []
举个例子
info = "hello,my name is Frank" print(info.splitlines()) #运行结果 ['hello,my name is Frank']
.startswith()
判断是否以指定字符串或字符开头，可指定索引范围，返回布尔值
def startswith(self, prefix, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.startswith(prefix[, start[, end]]) -> bool
Return True if S starts with the specified prefix, False otherwise.
With optional start, test S beginning at that position.
With optional end, stop comparing S at that position.
prefix can also be a tuple of strings to try.
"""
return False
举个例子
info = "hello,my name is Frank"
print(info.startswith("he"))
print(info.startswith("e"))
print(info.startswith("m",6,-1))
#运行结果
True
False
True
.swapcase()
将字符串中的大小写互换
def swapcase(self): # real signature unknown; restored from __doc__
"""
S.swapcase() -> str
Return a copy of S with uppercase characters converted to lowercase
and vice versa.
"""
return ""
举个例子
info = "Hello,My name is Frank" print(info.swapcase()) #运行结果 hELLO,mY NAME IS fRANK
.zfill（）
指定字符串宽度，不足的右边填 “0”
def zfill(self, width): # real signature unknown; restored from __doc__
"""
S.zfill(width) -> str
Pad a numeric string S with zeros on the left, to fill a field
of the specified width. The string S is never truncated.
"""
return ""
举个例子
info = "Hello,My name is Frank" print(info.zfill(50)) #运行结果 0000000000000000000000000000Hello,My name is Frank
四、列表
列表是由一系列按特定顺序排列的元素组成。在 python 中，用方括号（[]），来表示列表，并用逗号来分割其中的元素，我们来看一下简单的列表，其 type 为 "list"
name = ['Frank','Caroline','Bob','Saber'] print(name) #直接打印会将中括号、引号和逗号都打印出来 print(name[1]) #添加索引可打印对应的值，从索引值从0开始 print(name[-1]) #打印最后一个元素 print(name[0:2]) #用冒号来切片,取右不取左 print(name[-2:]) #冒号右边不写代表一直打印到最后一个 print(name[:1]) #冒号左边不写代表从第“0”个开始打印
常见方法如下：
.index()
查找对应元素的索引值，返回索引值，可以指定索引范围来查找，查找不到会报错
def index(self, value, start=None, stop=None): # real signature unknown; restored from __doc__
"""
L.index(value, [start, [stop]]) -> integer -- return first index of value.
Raises ValueError if the value is not present.
"""
return 0
举个例子
name = ['Frank','Caroline','Bob','Saber']
print(name.index("Frank"))
print(name.index("Bob",1,-1))
#运行结果
0
2
.count(）
计算某个元素的个数
def count(self, value): # real signature unknown; restored from __doc__
""" L.count(value) -> integer -- return number of occurrences of value """
return 0
举个例子
name = ['Frank','Caroline','Bob','Saber','Frank']
print(name.count('Frank'))
#运行结果
2
.append()
在列表的最后添加元素
def append(self, p_object): # real signature unknown; restored from __doc__
""" L.append(object) -> None -- append object to end """
pass
举个例子
name = ['Frank','Caroline','Bob','Saber','Frank']
name.append('Mei')
print(name)
#运行结果
['Frank', 'Caroline', 'Bob', 'Saber', 'Frank', 'Mei']
.clear()
清空列表
def clear(self): # real signature unknown; restored from __doc__
""" L.clear() -> None -- remove all items from L """
pass
举个例子
name = ['Frank','Caroline','Bob','Saber','Frank'] name.clear() print(name) #运行结果 []
.copy()
复制列表
def copy(self): # real signature unknown; restored from __doc__
""" L.copy() -> list -- a shallow copy of L """
return []
举个例子
name = ['Saber','Frank',1,2,[3,4]] name_cp = name.copy() print(name_cp) name[0]='Tom' name[3]='7' name[4][0]='8' print(name) print(name_cp) #运行结果 ['Saber', 'Frank', 1, 2, [3, 4]] ['Tom', 'Frank', 1, '7', ['8', 4]] ['Saber', 'Frank', 1, 2, ['8', 4]]
我们会发现，我们给 name[0]、name[3]、和 name[4][0] 都重新赋值了，为什么我重新赋值的 name[4][0] 会影响到我复制的列表的呢？
首先我们来看一下这个复制图解：
我们在复制的时候，新复制的列表都会指向被复制列表的地址空间，name[4] 和 name_cp[4] 本身也是个列表，它们指向的是同一个列表地址空间。我们来看一下给 name 列表重新赋值后，地址空间的变化：
重新赋值后，内存给 name[3]、name[0]、name[4][0] 都重新开辟了一块内存空间，name[0] 指向了内存地址 38703432，name[3] 指向了内存地址 1400943960，而 name[4] 还是指向 37092936, 但是内存地址 37092936 指向 name[4][0] 内存地址发生了变化，指向了 1400944350，所以，在列表中的列表我们给它重新赋值的时候，也会改变复制列表的值，因为它们的列表里的列表都是指向同一块地址空间。那么如果我们想完全复制怎么办呢？
可以调用函数 deepcopy().
import copy name = ['Saber','Frank',1,2,[3,4]] name_cp=copy.deepcopy(name) name[4][0]=5 print(name) print(name_cp) #运行结果 ['Saber', 'Frank', 1, 2, [5, 4]] ['Saber', 'Frank', 1, 2, [3, 4]]
这样会给复制后的列表中的列表重新开辟一个地址空间，然后指向列表中列表的元素的地址空间，这样你怎么改变原列表 name，name_copy 都不会改变。
.extend()
函数用于在列表末尾一次性追加另一个序列中的多个值（用新列表扩展原来的列表）。
def extend(self, iterable): # real signature unknown; restored from __doc__
""" L.extend(iterable) -> None -- extend list by appending elements from the iterable """
pass
举个例子
name = ['Saber','Frank'] nameto = ['Mei','Jack'] name.extend(nameto) print(name) #运行结果 ['Saber', 'Frank', 'Mei', 'Jack']
insert()
插入元素，需要指定索引值来插入
def insert(self, index, p_object): # real signature unknown; restored from __doc__
""" L.insert(index, object) -- insert object before index """
pass
举个例子
name = ['Saber','Frank'] name.insert(0,'Jack') print(name) #运行结果 ['Jack', 'Saber', 'Frank']
.pop()
弹出元素，默认弹出最后一个元素，可以指定索引，弹出对应的元素，当列表弹空或者没有指定的索引值会报错，并返回弹出的值
def pop(self, index=None): # real signature unknown; restored from __doc__
"""
L.pop([index]) -> item -- remove and return item at index (default last).
Raises IndexError if list is empty or index is out of range.
"""
pass
举个例子
name = ['Saber','Frank','Caroline','Jack'] name.pop() print(name) name = ['Saber','Frank','Caroline','Jack'] name.pop(1) print(name) #运行结果 ['Saber', 'Frank', 'Caroline'] ['Saber', 'Caroline', 'Jack']
.remove()
移除指定的元素
def remove(self, value): # real signature unknown; restored from __doc__
"""
L.remove(value) -> None -- remove first occurrence of value.
Raises ValueError if the value is not present.
"""
pass
举个例子
name = ['Saber','Frank','Caroline','Jack']
name.remove('Frank')
print(name)
#运行结果
['Saber', 'Caroline', 'Jack']
.reverse()
列表反转，永久修改
def reverse(self): # real signature unknown; restored from __doc__
""" L.reverse() -- reverse *IN PLACE* """
pass
举个例子
name = ['Saber','Frank','Caroline','Jack'] name.reverse() print(name) #运行结果 ['Jack', 'Caroline', 'Frank', 'Saber']
.sort()
对列表进行排序，永久修改，如果列表中同时存在不同类型的数据，则不能排序，比如含有整型和字符串，传递 reverse=True 可以倒着排序。
def sort(self, key=None, reverse=False): # real signature unknown; restored from __doc__
""" L.sort(key=None, reverse=False) -> None -- stable sort *IN PLACE* """
pass
举个例子
name = ['Saber','Frank','Caroline','Jack','1','abc','xyz'] name.sort() print(name) name.sort(reverse=True) print(name) #运行结果 ['1', 'Caroline', 'Frank', 'Jack', 'Saber', 'abc', 'xyz'] ['xyz', 'abc', 'Saber', 'Jack', 'Frank', 'Caroline', '1'] number = [1,2,3,42,12,32,43,543] number.sort() print(number) number.sort(reverse=True) print(number) #运行结果 [1, 2, 3, 12, 32, 42, 43, 543] [543, 43, 42, 32, 12, 3, 2, 1]
五、元组
元组和列表类似，不同的是元组的元素是不能修改的，使用小括号 "()" 括起来，用逗号 "," 分开，其 type 为 tuple
number = (1,2,2,2,1) print(type(number)) print(number[0]) print(number[-1]) print(number[1:]) #运行结果 <class 'tuple'> 1 1 (2, 2, 2, 1)
常见方法如下：
.count()
计算指定元素的个数
def count(self, value): # real signature unknown; restored from __doc__
""" T.count(value) -> integer -- return number of occurrences of value """
return 0
举个例子
number = (1,2,2,2,1) print(number.count(2)) #运行结果 3
.index(）
查找指定元素的索引，可以指定索引范围来查找
def index(self, value, start=None, stop=None): # real signature unknown; restored from __doc__
"""
T.index(value, [start, [stop]]) -> integer -- return first index of value.
Raises ValueError if the value is not present.
"""
return 0
举个例子
number = (1,2,2,2,1) print(number.index(2)) print(number.index(2,2,-1)) #运行结果 1 2
六、集合
集合是一系列无序的元素组成，所有你不能使用索引值，在打印的时候，元组是自然排序，天然去重的，其 type 为 set
number = {1,2,3,4,4,5,6}
number1 = {1,6,2,1,8,9,10}
print(number)
print(number1)
#运行结果
{1, 2, 3, 4, 5, 6}
{1, 2, 6, 8, 9, 10}
常用方法如下
.remove()
移除指定的元素
def remove(self, *args, **kwargs): # real signature unknown
"""
Remove an element from a set; it must be a member.
If the element is not a member, raise a KeyError.
"""
pass
举个例子
number = {1,2,3,4,4,5,6}
print(number)
number.remove(1)
print(number)
#运行结果
{1, 2, 3, 4, 5, 6}
{2, 3, 4, 5, 6}
.pop()
弹出排序过后的第一个元素
def pop(self, *args, **kwargs): # real signature unknown
"""
Remove and return an arbitrary set element.
Raises KeyError if the set is empty.
"""
pass
举个例子
number = {1,2,3,4,4,5,6}
print(number)
number_pop = number.pop()
print(number_pop)
print(number)
#运行结果
{1, 2, 3, 4, 5, 6}
1
{2, 3, 4, 5, 6}
.clear()
清空列表返回 set()
def clear(self, *args, **kwargs): # real signature unknown
""" Remove all elements from this set. """
pass
举个例子
number = {1,2,3,4,4,5,6}
print(number)
number.clear()
print(number)
#运行结果
{1, 2, 3, 4, 5, 6}
set()
.copy()
复制集合
def copy(self, *args, **kwargs): # real signature unknown
""" Return a shallow copy of a set. """
pass
举个例子
number = {1,2,3,4,4,5,6}
print(number)
number2 = number.copy()
number.pop()
print(number)
print(number2)
#运行结果
{1, 2, 3, 4, 5, 6}
{2, 3, 4, 5, 6}
{1, 2, 3, 4, 5, 6}
.add()
添加元素
def add(self, *args, **kwargs): # real signature unknown
"""
Add an element to a set.
This has no effect if the element is already present.
"""
pass
举个例子
number = {1,2,3,4,4,5,6}
print(number)
number.add(7)
print(number)
#运行结果
{1, 2, 3, 4, 5, 6}
{1, 2, 3, 4, 5, 6, 7}
.difference()
求差集，可以用 “-” 代替
def difference(self, *args, **kwargs): # real signature unknown
"""
Return the difference of two or more sets as a new set.
(i.e. all elements that are in this set but not the others.)
"""
pass
举个例子
number = {1,2,3,4,5,6,8,9}
number1 = {2,3,8,9,11,12,10}
print(number.difference(number1))
print(number1.difference(number))
print(number - number1)
print(number1 - number)
##运行结果
{1, 4, 5, 6}
{10, 11, 12}
{1, 4, 5, 6}
{10, 11, 12}
.union()
求并集，可用 “|” 代替
def union(self, *args, **kwargs): # real signature unknown
"""
Return the union of sets as a new set.
(i.e. all elements that are in either set.)
"""
pass
举个例子
number = {1,2,3,4,5,6,8,9}
number1 = {2,3,8,9,11,12,10}
print(number.union(number1))
print(number | number1)
#运行结果
{1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12}
{1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12}
difference_update.()
差异更新，没有返回值，直接修改集合
def difference_update(self, *args, **kwargs): # real signature unknown
""" Remove all elements of another set from this set. """
pass
举个例子
number = {1,2,3,4,5,6,8,9,13}
number1 = {2,3,8,9,11,12,10}
number.difference_update(number1)
print(number)
#运行结果
{1, 4, 5, 6, 13}
.discard()
移除指定元素，如果集合内没有指定的元素，就什么都不做
def discard(self, *args, **kwargs): # real signature unknown
"""
Remove an element from a set if it is a member.
If the element is not a member, do nothing.
"""
pass
举个例子
number = {1,2,3,4,5,6,8,9,13}
number.discard(1)
print(number)
#运行结果
{2, 3, 4, 5, 6, 8, 9, 13}
.intersection()
交集，可以用 "&" 代替
def intersection(self, *args, **kwargs): # real signature unknown
"""
Return the intersection of two sets as a new set.
(i.e. all elements that are in both sets.)
"""
pass
举个例子
number = {1,2,3,4,5,6,8,9,13}
number1 = {1,2,3,4,5,13,16,17}
print(number.intersection(number1))
print(number & number1)
#运行结果
{1, 2, 3, 4, 5, 13}
{1, 2, 3, 4, 5, 13}
.intersection_update()
交集更新，没有返回值，直接修改集合
def intersection_update(self, *args, **kwargs): # real signature unknown
""" Update a set with the intersection of itself and another. """
pass
举个例子
number = {1,2,3,4,5,6,8,9,13}
number1 = {1,2,3,4,5,13,16,17}
number.intersection_update(number1)
print(number)
#运行结果
{1, 2, 3, 4, 5, 13}
isdisjoint()
当两个集合没有交集的时候，返回 True，否则返回 False
def isdisjoint(self, *args, **kwargs): # real signature unknown
""" Return True if two sets have a null intersection. """
pass
举个例子
number = {1,2,3,4,5,6,8,9,13}
number1 = {16,17}
print(number.isdisjoint(number1))
#运行结果
True
number = {1,2,3,4,5,6,8,9,13,16}
number1 = {16,17}
#运行结果
False
.issubset()
当有 2 个集合 A 和 B，A.issubset(B)，A 是否被 B 包含，如果是则返回 True，否则返回 False
def issubset(self, *args, **kwargs): # real signature unknown
""" Report whether another set contains this set. """
pass
举个例子
number = {1,2,3,4,5,6,8,9,13,16,17}
number1 = {16,17}
print(number1.issubset(number))
#运行结果
True
.issuperset(）
当有 2 个集合 A 和 B，A.issuperset(B)，A 是否包含 B，如果包含则返回 True，否则返回 False
def issuperset(self, *args, **kwargs): # real signature unknown
""" Report whether this set contains another set. """
pass
举个例子
number = {1,2,3,4,5,6,8,9,13,16,17}
number1 = {16,17}
print(number.issuperset(number1))
#运行结果
True
.symmetric_difference()
取两个集合的差集，即取两个集合中对方都没有的元素
def symmetric_difference(self, *args, **kwargs): # real signature unknown
"""
Return the symmetric difference of two sets as a new set.
(i.e. all elements that are in exactly one of the sets.)
"""
pass
举个例子
number = {1,2,3,4,5,6,8,9,13,16,17}
number1 = {16,17,18,19}
print(number.symmetric_difference(number1))
#运行结果
{1, 2, 3, 4, 5, 6, 8, 9, 13, 18, 19}
.symmetric_difference_update()
取两个集合的差集，即取两个集合中对方都没有的元素, 并更新到集合中
def symmetric_difference_update(self, *args, **kwargs): # real signature unknown
""" Update a set with the symmetric difference of itself and another. """
pass
举个例子
number = {1,2,3,4,5,6,8,9,13,16,17}
number1 = {16,17,18,19}
number.symmetric_difference_update(number1)
print(number)
#运行结果
{1, 2, 3, 4, 5, 6, 8, 9, 13, 18, 19}
.update()
取两个集合的并集，并更新到集合中
def update(self, *args, **kwargs): # real signature unknown
""" Update a set with the union of itself and others. """
pass
举个例子
number = {1,2,3,4,5,6,8,9,13,16,17}
number1 = {16,17,18,19}
number.update(number1)
print(number)
#运行结果
{1, 2, 3, 4, 5, 6, 8, 9, 13, 16, 17, 18, 19}
七、字典
在 python 里面，字典就是一系列的 键 - 值，每个值都与一个值是一一对应的，键可以是数字、字符串、列表和字典。实际上，可以将任何 python 对象用作字典的值。
info = {
'name':'Frank',
'age':23,
'hobbby':'reading',
'address':'Shanghai',
}
print(info)
print(info['age'])
#运行结果
{'name': 'Frank', 'age': 23, 'hobbby': 'reading', 'address': 'Shanghai'}
23
方法如下：
.keys()
取出字典的键
def keys(self): # real signature unknown; restored from __doc__
""" D.keys() -> a set-like object providing a view on D's keys """
pass
举个例子
info = {
'name':'Frank',
'age':23,
'hobbby':'reading',
'address':'Shanghai',
}
print(info.keys())
#运行结果
dict_keys(['name', 'age', 'hobbby', 'address'])
.values()
取出字典的值
def values(self): # real signature unknown; restored from __doc__
""" D.values() -> an object providing a view on D's values """
pass
举个例子
info = {
'name':'Frank',
'age':23,
'hobbby':'reading',
'address':'Shanghai',
}
#运行结果
print(info.values())
.pop()
弹出一个键值对，必须指定键
举个例子
info = {
'name':'Frank',
'age':23,
'hobbby':'reading',
'address':'Shanghai',
}
info.pop('name')
print(info)
#运行结果
{'age': 23, 'hobbby': 'reading', 'address': 'Shanghai'}
.clear()
清空字典里的键值对
def clear(self): # real signature unknown; restored from __doc__
""" D.clear() -> None. Remove all items from D. """
pass
举个例子
info = {
'name':'Frank',
'age':23,
'hobbby':'reading',
'address':'Shanghai',
}
info.clear()
print(info)
#运行结果
{}
.update()
更新字典，如果有 2 个字典 A 和 B，A.update(B),A 和 B 相同的键的值会被 B 更新，而 B 中没有的键值对会被添加到 A 中
def update(self, E=None, **F): # known special case of dict.update
"""
D.update([E, ]**F) -> None. Update D from dict/iterable E and F.
If E is present and has a .keys() method, then does: for k in E: D[k] = E[k]
If E is present and lacks a .keys() method, then does: for k, v in E: D[k] = v
In either case, this is followed by: for k in F: D[k] = F[k]
"""
pass
举个例子
info = {
'name':'Frank',
'age':23,
'hobby':'reading',
'address':'Shanghai',
}
info_new = {
'age':24,
'hobby':'sleeping',
'QQ':'110110',
}
info.update(info_new)
print(info)
#运行结果
{'name': 'Frank', 'age': 24, 'hobby': 'sleeping', 'address': 'Shanghai', 'QQ': '110110'}
.copy()
复制字典
info = {
'name':'Frank',
'age':23,
'hobby':['reading','sleep'],
'address':'Shanghai',
}
info_new = info.copy()
info['name']='Jack'
info['hobby'][0]='writing'
print(info)
print(info_new)
#运行结果
{'name': 'Jack', 'age': 23, 'hobby': ['writing', 'sleep'], 'address': 'Shanghai'}
{'name': 'Frank', 'age': 23, 'hobby': ['writing', 'sleep'], 'address': 'Shanghai'}
我们会发现和列表中的 copy 一样，也存在字典里面的列表的元素被修改后，复制的字典也会自动修改，这个原因其实和前面的是一样的，我们这里也可以使用 deep.copy
import copy
info = {
'name':'Frank',
'age':23,
'hobby':['reading','sleep'],
'address':'Shanghai',
}
info_new = copy.deepcopy(info)
info['name']='Jack'
info['hobby'][0]='writing'
print(info)
print(info_new)
#运行结果
{'name': 'Jack', 'age': 23, 'hobby': ['writing', 'sleep'], 'address': 'Shanghai'}
{'name': 'Frank', 'age': 23, 'hobby': ['reading', 'sleep'], 'address': 'Shanghai'}
那字典里的字典会不会出现相同的问题呢？
info = {
'name':'Frank',
'age':23,
'hobby':['reading','sleep'],
'address':'Shanghai',
'language':{1:'Python',2:'Go'},
}
info_new = info.copy()
info['name']='Jack'
info['hobby'][0]='writing'
info['language'][2]='Java'
print(info)
print(info_new)
#运行结果
{'name': 'Jack', 'age': 23, 'hobby': ['writing', 'sleep'], 'address': 'Shanghai', 'language': {1: 'Python', 2: 'Java'}}
{'name': 'Frank', 'age': 23, 'hobby': ['writing', 'sleep'], 'address': 'Shanghai', 'language': {1: 'Python', 2: 'Java'}}
答案是，是的，当我们想在修改原字典的时候，复制的字典保持不变，还是可以使用 deep.copy 来解决这个问题。
import copy
info = {
'name':'Frank',
'age':23,
'hobby':['reading','sleep'],
'address':'Shanghai',
'language':{1:'Python',2:'Go'},
}
info_new = copy.deepcopy(info)
info['name']='Jack'
info['hobby'][0]='writing'
info['language'][2]='Java'
print(info)
print(info_new)
#运行结果
{'name': 'Jack', 'age': 23, 'hobby': ['writing', 'sleep'], 'address': 'Shanghai', 'language': {1: 'Python', 2: 'Java'}}
{'name': 'Frank', 'age': 23, 'hobby': ['reading', 'sleep'], 'address': 'Shanghai', 'language': {1: 'Python', 2: 'Go'}}
这也是我们常说的深浅 copy！
.fromkeys()
用来创建一个新的字典
def fromkeys(*args, **kwargs): # real signature unknown
""" Returns a new dict with keys from iterable and values equal to value. """
pass
举个例子
key = (1,2,3,4,5)
value = 'Python'
print(dict.fromkeys(key,value))
#运行结果
{1: 'Python', 2: 'Python', 3: 'Python', 4: 'Python', 5: 'Python'}
.get()
根据键返回值，没有键则返回 None
info = {
'name':'Frank',
'age':23,
'hobby':['reading','sleep'],
'address':'Shanghai',
}
print(info.get('hobby'))
#运行结果
['reading', 'sleep']
.items()
返回 dict_items()，一般结合 for 循环使用
info = {
'name':'Frank',
'age':23,
'hobby':['reading','sleep'],
'address':'Shanghai',
}
print(info.items())
#运行结果
dict_items([('name', 'Frank'), ('age', 23), ('hobby', ['reading', 'sleep']), ('address', 'Shanghai')])
info = {
'name':'Frank',
'age':23,
'hobby':['reading','sleep'],
'address':'Shanghai',
}
for k,v in info.items():
print(k,"---",v)
#运行结果
name --- Frank
age --- 23
hobby --- ['reading', 'sleep']
address --- Shanghai
.popitem()
弹出最后一个键值, 会返回一个元组，当弹空字典会报错
def popitem(self): # real signature unknown; restored from __doc__
"""
D.popitem() -> (k, v), remove and return some (key, value) pair as a
2-tuple; but raise KeyError if D is empty.
"""
pass
举个例子
info = {
'name':'Frank',
'age':23,
'hobby':['reading','sleep'],
'address':'Shanghai',
}
print(info.popitem())
info.popitem()
print(info)
#举个例子
('address', 'Shanghai')
{'name': 'Frank', 'age': 23}
.setdefault(key,value）
如果键在字典中，则返回这个键的值，如果不在字典中，则向字典中插入这个键，并返回 value，默认 value 位 None
举个例子
info = {
'name':'Frank',
'age':23,
'hobby':['reading','sleep'],
}
print(info.setdefault('name')) #存在键name,返回值
print(info)
print(info.setdefault('address','shanghai')) #不存在键address,返回'shanghai'，添加键值对
print(info)
print(info.setdefault('QQ')) #不存在键QQ，添加键QQ，返回None
print(info)
#运行结果
Frank
{'name': 'Frank', 'age': 23, 'hobby': ['reading', 'sleep']}
shanghai
{'name': 'Frank', 'age': 23, 'hobby': ['reading', 'sleep'], 'address': 'shanghai'}
None
{'name': 'Frank', 'age': 23, 'hobby': ['reading', 'sleep'], 'address': 'shanghai', 'QQ': None}