字符串
Python对字符串的处理内置了很多高效的函数，非常方便功能很强大。
"hello world"
字符串七种常用功能：
- 连接和合并 + join
- 移除空白 strip
- 分割 split
- 长度 len()
- 索引 str[index]
- 切片 str[0,7]
- 替换 replace()
1.1 字符串的连接和合并
连接和合并
相加 //两个字符串可以很方便的通过'+'连接起来
合并//用join方法
text1="David" text2="J" v=text1+text2 print(v) v1="_".join(v) print(v1) # DavidJ # D_a_v_i_d_J
1.2 字符串的索引、切片
索引
切片
text="David J" # v1=text[0] # v1=text[0:1] #0=< <1 # v1=text[0:-1] # v1=text[0:len(text)+1] v1=text[1:] print(v1)
1.3 字符串的分割
普通的分割，用split
split只能做非常简单的分割，而且不支持多个分隔
text = '1+2+4'
v1,v2,v3=text.split(+)
r表示不转义,分隔符可以是;或者,或者空格后面跟0个多个额外的空格，然后按照这个模式去分割
# 分割
phone='400-800-800-1234'
print(phone.split('-'))
##['400', '800', '800', '1234']
#复杂分割 import re
import re
text="hello world; python,David J like it!"
v=re.split(r'[;,!s]s*',text)
print(v)
##['hello world', 'python', 'David J like it', '']
1.4 字符串的查找和匹配
一般查找 find
我们可以很方便的在长的字符串里面查找子字符串，会返回子字符串所在位置的索引, 若找不到返回-1
复杂的匹配可参考re.match
#字符串的查找和匹配
text="布尔值分别有什么?"
v1=text.find("布尔")
v2=text.find("尔")
v3=text.find("尔",3)
v4=text.find("bool")
print(v1,v2,v3,v4)
##0 1 -1 -1
#复杂的匹配可参考使用re.match
1.5 字符串的替换
普通的替换,用replace就可以
若要处理复杂的或者多个的替换，需要用到re模块的sub函数
#字符串的替换
text="David J like zhuzhu"
v1=text.replace("vid","wei")
print(v1)
import re
text2="Shandong 37,Shanxi 14"
v2=re.sub(r'd+','100',text2)
print(v2)
# Dawei J like zhuzhu
# Shandong 100,Shanxi 100
1.6 字符串中去掉一些字符
去除空格：对文本处理的时候比如从文件中读取一行或获取用户名输入后，去除字符串首尾的空格，table /t或者是换行符/n
text=" hello everyone, i am David J.
"
print(text)
v1=text.strip()
v2=text.rstrip()
v3=text.lstrip()
v4=text.strip(" ")
print(v1)
print(v2)
print(v3)
print(v4)
复杂的文本清理,可以利用str.translate
字符串遍历
for 变量名 in 字符串：
变量名
两种遍历
for i in range(0,100,1):
for i in range(100,0,-1):
print(i)
字符串特性注意
字符串一旦创建，不能修改
一旦修改或拼接，都会重新生成新字符串
字符串各方法源码及注释：
class str(basestring):
"""
str(object='') -> string
Return a nice string representation of the object.
If the argument is a string, the return value is the same object.
"""
def capitalize(self):
""" 首字母变大写 """
"""
S.capitalize() -> string
Return a copy of the string S with only its first character
capitalized.
"""
return ""
def center(self, width, fillchar=None):
""" 内容居中，width：总长度；fillchar：空白处填充内容，默认无 """
"""
S.center(width[, fillchar]) -> string
Return S centered in a string of length width. Padding is
done using the specified fill character (default is a space)
"""
return ""
def count(self, sub, start=None, end=None):
""" 子序列个数 """
"""
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
def decode(self, encoding=None, errors=None):
""" 解码 """
"""
S.decode([encoding[,errors]]) -> object
Decodes S using the codec registered for encoding. encoding defaults
to the default encoding. errors may be given to set a different error
handling scheme. Default is 'strict' meaning that encoding errors raise
a UnicodeDecodeError. Other possible values are 'ignore' and 'replace'
as well as any other name registered with codecs.register_error that is
able to handle UnicodeDecodeErrors.
"""
return object()
def encode(self, encoding=None, errors=None):
""" 编码，针对unicode """
"""
S.encode([encoding[,errors]]) -> object
Encodes S using the codec registered for encoding. encoding defaults
to the default encoding. 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 is able to handle UnicodeEncodeErrors.
"""
return object()
def endswith(self, suffix, start=None, end=None):
""" 是否以 xxx 结束 """
"""
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
def expandtabs(self, tabsize=None):
""" 将tab转换成空格，默认一个tab转换成8个空格 """
"""
S.expandtabs([tabsize]) -> string
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 ""
def find(self, sub, start=None, end=None):
""" 寻找子序列位置，如果没找到，返回 -1 """
"""
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
def format(*args, **kwargs): # known special case of str.format
""" 字符串格式化，动态参数，将函数式编程时细说 """
"""
S.format(*args, **kwargs) -> string
Return a formatted version of S, using substitutions from args and kwargs.
The substitutions are identified by braces ('{' and '}').
"""
pass
def index(self, sub, start=None, end=None):
""" 子序列位置，如果没找到，报错 """
S.index(sub [,start [,end]]) -> int
Like S.find() but raise ValueError when the substring is not found.
"""
return 0
def isalnum(self):
""" 是否是字母和数字 """
"""
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
def isalpha(self):
""" 是否是字母 """
"""
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
def isdigit(self):
""" 是否是数字 """
"""
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
def islower(self):
""" 是否小写 """
"""
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
def isspace(self):
"""
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
def istitle(self):
"""
S.istitle() -> bool
Return True if S is a titlecased string and there is at least one
character in S, i.e. uppercase characters may only follow uncased
characters and lowercase characters only cased ones. Return False
otherwise.
"""
return False
def isupper(self):
"""
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
def join(self, iterable):
""" 连接 """
"""
S.join(iterable) -> string
Return a string which is the concatenation of the strings in the
iterable. The separator between elements is S.
"""
return ""
def ljust(self, width, fillchar=None):
""" 内容左对齐，右侧填充 """
"""
S.ljust(width[, fillchar]) -> string
Return S left-justified in a string of length width. Padding is
done using the specified fill character (default is a space).
"""
return ""
def lower(self):
""" 变小写 """
"""
S.lower() -> string
Return a copy of the string S converted to lowercase.
"""
return ""
def lstrip(self, chars=None):
""" 移除左侧空白 """
"""
S.lstrip([chars]) -> string or unicode
Return a copy of the string S with leading whitespace removed.
If chars is given and not None, remove characters in chars instead.
If chars is unicode, S will be converted to unicode before stripping
"""
return ""
def partition(self, sep):
""" 分割，前，中，后三部分 """
"""
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
def replace(self, old, new, count=None):
""" 替换 """
"""
S.replace(old, new[, count]) -> string
Return a copy of string 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 ""
def rfind(self, sub, start=None, end=None):
"""
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
def rindex(self, sub, start=None, end=None):
"""
S.rindex(sub [,start [,end]]) -> int
Like S.rfind() but raise ValueError when the substring is not found.
"""
return 0
def rjust(self, width, fillchar=None):
"""
S.rjust(width[, fillchar]) -> string
Return S right-justified in a string of length width. Padding is
done using the specified fill character (default is a space)
"""
return ""
def rpartition(self, sep):
"""
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
def rsplit(self, sep=None, maxsplit=None):
"""
S.rsplit([sep [,maxsplit]]) -> list of strings
Return a list of the words in the string 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 or is None, any whitespace string
is a separator.
"""
return []
def rstrip(self, chars=None):
"""
S.rstrip([chars]) -> string or unicode
Return a copy of the string S with trailing whitespace removed.
If chars is given and not None, remove characters in chars instead.
If chars is unicode, S will be converted to unicode before stripping
"""
return ""
def split(self, sep=None, maxsplit=None):
""" 分割， maxsplit最多分割几次 """
"""
S.split([sep [,maxsplit]]) -> list of strings
Return a list of the words in the string 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 []
def splitlines(self, keepends=False):
""" 根据换行分割 """
"""
S.splitlines(keepends=False) -> 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 []
def startswith(self, prefix, start=None, end=None):
""" 是否起始 """
"""
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
def strip(self, chars=None):
""" 移除两段空白 """
"""
S.strip([chars]) -> string or unicode
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.
If chars is unicode, S will be converted to unicode before stripping
"""
return ""
def swapcase(self):
""" 大写变小写，小写变大写 """
"""
S.swapcase() -> string
Return a copy of the string S with uppercase characters
converted to lowercase and vice versa.
"""
return ""
def title(self):
"""
S.title() -> string
Return a titlecased version of S, i.e. words start with uppercase
characters, all remaining cased characters have lowercase.
"""
return ""
def translate(self, table, deletechars=None):
"""
转换，需要先做一个对应表，最后一个表示删除字符集合
intab = "aeiou"
outtab = "12345"
trantab = maketrans(intab, outtab)
str = "this is string example....wow!!!"
print str.translate(trantab, 'xm')
"""
"""
S.translate(table [,deletechars]) -> string
Return a copy of the string S, where all characters occurring
in the optional argument deletechars are removed, and the
remaining characters have been mapped through the given
translation table, which must be a string of length 256 or None.
If the table argument is None, no translation is applied and
the operation simply removes the characters in deletechars.
"""
return ""
def upper(self):
"""
S.upper() -> string
Return a copy of the string S converted to uppercase.
"""
return ""
def zfill(self, width):
"""方法返回指定长度的字符串，原字符串右对齐，前面填充0。"""
"""
S.zfill(width) -> string
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 ""
def _formatter_field_name_split(self, *args, **kwargs): # real signature unknown
pass
def _formatter_parser(self, *args, **kwargs): # real signature unknown
pass
def __add__(self, y):
""" x.__add__(y) <==> x+y """
pass
def __contains__(self, y):
""" x.__contains__(y) <==> y in x """
pass
def __eq__(self, y):
""" x.__eq__(y) <==> x==y """
pass
def __format__(self, format_spec):
"""
S.__format__(format_spec) -> string
Return a formatted version of S as described by format_spec.
"""
return ""
def __getattribute__(self, name):
""" x.__getattribute__('name') <==> x.name """
pass
def __getitem__(self, y):
""" x.__getitem__(y) <==> x[y] """
pass
def __getnewargs__(self, *args, **kwargs): # real signature unknown
pass
def __getslice__(self, i, j):
"""
x.__getslice__(i, j) <==> x[i:j]
Use of negative indices is not supported.
"""
pass
def __ge__(self, y):
""" x.__ge__(y) <==> x>=y """
pass
def __gt__(self, y):
""" x.__gt__(y) <==> x>y """
pass
def __hash__(self):
""" x.__hash__() <==> hash(x) """
pass
def __init__(self, string=''): # known special case of str.__init__
"""
str(object='') -> string
Return a nice string representation of the object.
If the argument is a string, the return value is the same object.
# (copied from class doc)
"""
pass
def __len__(self):
""" x.__len__() <==> len(x) """
pass
def __le__(self, y):
""" x.__le__(y) <==> x<=y """
pass
def __lt__(self, y):
""" x.__lt__(y) <==> x<y """
pass
def __mod__(self, y):
""" x.__mod__(y) <==> x%y """
pass
def __mul__(self, n):
""" x.__mul__(n) <==> x*n """
pass
@staticmethod # known case of __new__
def __new__(S, *more):
""" T.__new__(S, ...) -> a new object with type S, a subtype of T """
pass
def __ne__(self, y):
""" x.__ne__(y) <==> x!=y """
pass
def __repr__(self):
""" x.__repr__() <==> repr(x) """
pass
def __rmod__(self, y):
""" x.__rmod__(y) <==> y%x """
pass
def __rmul__(self, n):
""" x.__rmul__(n) <==> n*x """
pass
def __sizeof__(self):
""" S.__sizeof__() -> size of S in memory, in bytes """
pass
def __str__(self):
""" x.__str__() <==> str(x) """
pass
str