自学python笔记 第一章

type( ):

>>> route = 866
>>> print(route,type(route))
     866 <class 'int'>  #运行结果

输入对象引用名就能打出对象：

>>> x ="a"
>>> y ="b"
>>> x
'a'
>>> x,y #必须用逗号隔开
('a', 'b')

元组长度len( ):

>>> x =["a","b","c","d"]
>>> y ="guo zhengbing"
>>> len(x)
4
>>> len(y)
13

.append( )操作指令：插入一个元素

>>> x =["aa","21","guozhengbing","asd1223"]
>>> x.append("gzb")
>>> x
['aa', '21', 'guozhengbing', 'asd1223', 'gzb']

数组里个数从0开始：

>>> x =["aa","21","guozhengbing","asd1223"]
>>> x.append("gzb")
>>> x
['aa', '21', 'guozhengbing', 'asd1223', 'gzb']
>>> x[0]
'aa'
>>> x[4]
'gzb'

直接用x[*] =_来修改列表元素：

>>> x
['aa', '21', 'guozhengbing', 'asd1223', 'gzb']
>>> x[0] =["study hard"]
>>> x
[['study hard'], '21', 'guozhengbing', 'asd1223', 'gzb']

身份操作符：is，若is两端引用同一对象，则为true，否则为false

>>> x =["aa","21","guozhengbing","asd1223"]
>>> y =["aa","21","guozhengbing","asd1223"]
>>> x is y
False
>>> y = x
>>> x is y
True

比较操作符：

>>> a =1
>>> b  =2
>>> c =3
>>> a <=b,b ==c,a !=c
(True, False, True)

成员操作符：

>>> x =["aa","21","guozhengbing","asd1223"]
>>> 21 in x
False
>>> "21" in x
True

>>> phrase ="hello world"
>>> "o" in phrase

逻辑运算符：and ,or ,not

>>> five =5
>>> two =2
>>> zero =0
>>> five and two
2
>>> two and zero
0  #and,or,not用short-circuit逻辑，返回决定结果的操作数，而不是布尔值
>>> two and zero
0
>>> five or two
5
>>> zero or five
5

if,while语句遍历列表：

for...in... 语句：

x =["aa","21","guozhengbing","asd1223"]
for i in x:
    print(i)
#输出结果为：
aa
21
guozhengbing
asd1223

+与+=在字符串中（在列表中也能加）：

>>> name = "guo">>> name + "zhengbing"
'guozhengbing'
>>> name +="zhengbing"
>>> name
'guozhengbing'

列表中+=与.append的区别:

>>> temp =["11","22","33"]
>>> temp +="guozhengbing"
>>> temp
['11', '22', '33', 'g', 'u', 'o', 'z', 'h', 'e', 'n', 'g', 'b', 'i', 'n', 'g']
>>> temp.append("guozhengbing")
>>> temp
['11', '22', '33', 'g', 'u', 'o', 'z', 'h', 'e', 'n', 'g', 'b', 'i', 'n', 'g', 'guozhengbing']

定义函数：

def function(msg):
    while True:
        try:
            i =int(input(msg))
            return i
        except ValueError as err:
            print(err)

age =function("enter your age:")

#结果
enter your age:2.5
invalid literal for int() with base 10: '2.5'
enter your age:25

Process finished with exit code 0