Python初学4-变量与运算符

àì夳堔傛蜴生んèń 2022-05-23 13:07 162阅读 0赞

**命名规则：**

**       1. 只能使用字母、数字、下划线。且首字母不能是数字。**

**        2.系统使用的关键字（保留关键字）不可以被使用。**

数字

>>> A=[1,2,3]
    >>> print(A)
    [1, 2, 3]
    >>> B=[2,3,4,5]
    >>> print(A*3+B)
    [1, 2, 3, 1, 2, 3, 1, 2, 3, 2, 3, 4, 5]
    >>> A*3+B
    [1, 2, 3, 1, 2, 3, 1, 2, 3, 2, 3, 4, 5]

字符

>>> a='java '
    >>> b = 'python'
    >>> a+b
    'java python'
    >>> c = a+b
    >>> print(c)
    java python
    >>> c[0]
    'j'
    >>> c[0:5]
    'java '
    >>> c[0]='J'
    
    Traceback (most recent call last):
      File "<pyshell#13>", line 1, in <module>
        c[0]='J'
    TypeError: 'str' object does not support item assignment
    >>>

组

>>> a=[1,2,3]
    >>> print(a[1])
    2
    >>> a[1]=4
    >>> print(a)
    [1, 4, 3]
    >>> a.append(6)
    >>> print(a)
    [1, 4, 3, 6]

>>> b=(1,2,3)
    >>> b.append(5)
    Traceback (most recent call last):
      File "<pyshell#25>", line 1, in <module>
        b.append(5)
    AttributeError: 'tuple' object has no attribute 'append'

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[20180609150002773]: /images/20220523/f9c685cde50041559f1b1d8eed8d7e38.png
[20180609150017491]: /images/20220523/d044592eed6b43c0ad8875c92c604d57.png
[20180609150028875]: /images/20220523/dd786bcb67e94d50a843aafef328a6c3.png
[20180609150042224]: /images/20220523/2b81804c3b4641e5893d0450626c96ad.png
[20180609150059300]: https://img-blog.csdn.net/20180609150059300
[201806091501093]: https://img-blog.csdn.net/201806091501093
[20180609150116691]: /images/20220523/6e944e65a9bb47da8b3bc926e58b5614.png