Python基础学习

Pyhton基础之列表

1. 创建列表

C:\Windows\system32>python
Python 3.9.5 (tags/v3.9.5:0a7dcbd, May  3 2021, 17:27:52) [MSC v.1928 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> num_list = [5,6,4,3,23,4,5,65,2,34,45,6,455,6,34,23]
>>> print(num_list)
[5, 6, 4, 3, 23, 4, 5, 65, 2, 34, 45, 6, 455, 6, 34, 23]
>>>

定义一个列表并赋值给了num_list，然后用print打印
2. 访问列表

>>> num_list = [5,6,4,3,23,4,5,65,2,34,45,6,455,6,34,23]
>>> print(num_list[1])
6
>>>

[1]索引，print打印num_list列表中的第2个元素

>>> number = ['one', 'two', 'three', 'four']
>>> print(number [1].title())
Two
>>>

打印的时候给了[1]还有title()函数让首字母大写

>>> number = ['one', 'two', 'three', 'four']
>>> print(number [-1].title())
Four
>>>

访问最后一个元素，并且大写
3. 修改列表

>>> number = ['one', 'two', 'three', 'four']
>>> number[0] = 'zero'
>>> print(number)
['zero', 'two', 'three', 'four']

修改列表元素

>>> number = ['one', 'two', 'three', 'four']
>>> number.append('five')
>>> print(number)
['one', 'two', 'three', 'four', 'five']
>>>

使用append()函数把元素加到列表末尾

>>> number = []
>>> number.append('one')
>>> number.append('two')
>>> number.append('three')
>>> number.append('four')
>>> print(number)
['one', 'two', 'three', 'four']
>>>

先定义一个空列表，然后逐个的添加列表元素

>>> number = ['one', 'two', 'three', 'four']
>>> number.insert(0,'zero')
>>> print(number)
['zero', 'one', 'two', 'three', 'four']
>>>

append()是在列表最后加元素，insert()函数，制定索引和值就可以添加值进列表

>>> number = ['one', 'two', 'three', 'four']
>>> del number [0]
>>> print(number)
['two', 'three', 'four']
>>>

del加索引直接删除元素

>>> number = ['one', 'two', 'three', 'four']
>>> popped_number = number.pop()
>>> print(number)
['one', 'two', 'three']
>>> print(popped_number)
four
>>>

pop()函数默认删除最后一个值，pop()删除后会返回删除的数据，方便查看删除的数据

>>> number = ['one', 'two', 'three', 'four']
>>> popped_first = number.pop(0)
>>> print('The first number I poppend was ' + popped_first.title() + '.')
The first number I poppend was One.
>>>

pop加索引，删除索引位置的值，如果删除错误会引起系列问题

>>> number = ['one', 'two', 'three', 'four']
>>> number.remove('two')
>>> print(number)
['one', 'three', 'four']
>>>

也可以使用remove()函数进行删除remove()只会删除一个值，如果列中存在多个一样值，是只会删除一个
4. 列表排序

>>> number = ['one', 'two', 'three', 'four']
>>> number.sort()
>>> print(number)
['four', 'one', 'three', 'two']
>>>

sort()函数会按照字母顺序排序，排序的修改是永久性的

>>> number = ['one', 'two', 'three', 'four']
>>> number.sort(reverse=True)
>>> print(number)
['two', 'three', 'one', 'four']
>>>

sort()函数传递参数reverse=True，进行倒序Z-A的排序

>>> number = ['one', 'two', 'three', 'four']
>>> print(sorted(number))
['four', 'one', 'three', 'two']
>>> print(number)
['one', 'two', 'three', 'four']
>>>

sorted()函数临时对列表进行排序，不会真实的改变列表顺序

>>> number = ['one', 'two', 'three', 'four']
>>> new_list = sorted(number, reverse=True)
>>> print(new_list)
['two', 'three', 'one', 'four']
>>> print(number)
['one', 'two', 'three', 'four']
>>>

sorted()函数配合reverse=True进行临时的倒序排序

>>> number = ['one', 'two', 'three', 'four']
>>> number.reverse()
>>> print(number)
['four', 'three', 'two', 'one']
>>>

reverse()函数会永久反转列表，可以再次使用反转函数

>>> number = ['one', 'two', 'three', 'four']
>>> len(number)
4
>>>

获取列的长度

>>> list1 = [1,5,7,9,12,3,45,6678,2345,45,567,23]
>>> for i in range(len(list1)-1):
...    for j in range(len(list1)-i-1):
...       if list1[j]>list1[j+1]:
...           list1[j],list1[j+1] = list1[j+1],list1[j]
...
>>> print(list1)
[1, 3, 5, 7, 9, 12, 23, 45, 45, 567, 2345, 6678]
>>>

进行循环比较然后排序
5. 遍历列表

>>> number = ['one', 'two', 'three', 'four']
>>> for list_number in number:
...  print(list_number)
...
one
two
three
four
>>>

for循环遍历列表
6. 创建数值列表

>>> for value in range(1,5):
...     print(value)
...
1
2
3
4
>>>

range()函数从指定的数开始，到结束

>>> numbers = list(range(1,6))
>>> print(numbers)
[1, 2, 3, 4, 5]
>>>

用函数list()把range()的结果转换为列表

>>> even_numbers = list(range(2,11,2))
>>> print(even_numbers)
[2, 4, 6, 8, 10]
>>>

range()函数，让每次增加2，从2开始直到11结束，指定步长

>>> squares = []
>>> for value in range(1,11):
...   square = value**2
...   squares.append(square)
...   print(squares)
...
[1]
[1, 4]
[1, 4, 9]
[1, 4, 9, 16]
[1, 4, 9, 16, 25]
[1, 4, 9, 16, 25, 36]
[1, 4, 9, 16, 25, 36, 49]
[1, 4, 9, 16, 25, 36, 49, 64]
[1, 4, 9, 16, 25, 36, 49, 64, 81]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
>>>

平方的例子

>>> squares = []
>>> for value in range(1,11):
...   squares.append(value**2)
...
>>> print(squares)
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
>>>

使用range()创建数字集，然后创建列表，其中包含10个整数

>>> number = [1,2,3,4,5,6,7,8,9,0]
>>> min(number)
0
>>> max(number)
9
>>> sum(number)
45
>>>

找出列表中最小、最大值和列表数值总和
7. 列表解析

>>> squares = [value**2 for value in range(1,11)]
>>> print(squares)
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
>>>

for循环和创建新值的代码合并，自动附加新元素
8. 切片

>>> number = ['one', 'two', 'three', 'four']
>>> print(number [0:3])
['one', 'two', 'three']
>>>

指定索引0-3，会分别输出0、1、2的值

>>> number = ['one', 'two', 'three', 'four']
>>> print(number [:3])
['one', 'two', 'three']
>>>

不指定第一个索引，将自动从列表头开始输出

>>> number = ['one', 'two', 'three', 'four']
>>> print(number [2:])
['three', 'four']
>>>

直接结束于列表尾，多长都会输出

>>> number = ['one', 'two', 'three', 'four']
>>> print(number [-2:])
['three', 'four']
>>>

使用负数索引也可以输出
9. 使用切片遍历列表

>>> number = ['one', 'two', 'three', 'four']
>>> for list_number in number[:3]:
...   print(list_number.title())
...
One
Two
Three
>>>

有的时候，列表太长，完全输出效率太低，切片输出部分值
10. 使用切片复制列表

>>> number = ['one', 'two', 'three', 'four']
>>> new_list = number [:]
>>> print(new_list)
['one', 'two', 'three', 'four']
>>>

[:]从第一个值开始，到最后的值结束，这样生成new_list是新的，与number是独立的，相当于复制，如果再次修改number的值，new_list是没有任何影响的
11. 使用切片翻转列表

12. 其他切片 *** 作

Python基础之元组

13. 创建元组并访问元素
14. 元组和列表转换

Python基础之字典

15. 创建字典并访问元素
16. 添加建值对
17. 修改字典中的值
18. 删除键值对
19. 遍历字典
20. 嵌套

Python基础之字符串

21. 字符串实 ***
22. 合并（拼接）字符串
23. 删除空白

Python基础之文件

24. 读取整个文件
25. 逐行读取
26. 使用文件的内容

Python基础之函数

27. 定义函数
28. 向函数传参
29. 返回值

Python基础之类

30. 创建和使用类
31. 继承