Python基础学习

1. 创建列表

C:Windowssystem32>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. 其他切片操作

13. 创建元组并访问元素
14. 元组和列表转换

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

21. 字符串实操
22. 合并（拼接）字符串
23. 删除空白

24. 读取整个文件
25. 逐行读取
26. 使用文件的内容

27. 定义函数
28. 向函数传参
29. 返回值

30. 创建和使用类
31. 继承