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

自学python笔记 第一章

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自学python笔记第一章