python day3

朱雀 2021-11-26 09:38 293阅读 0赞

p33
    
    1 列表的创建：
     >>> a = [0,1,2,3,"day"]
    >>> a[0]
    0
    >>> a[3]
    3
    >>> a[4]
    'day'
    >>> 
    
    2  用list 转化成列表：
    >>> a = list(range(10))
    >>> a
    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
    >>> a = list("renshanwen")
    >>> a
    ['r', 'e', 'n', 's', 'h', 'a', 'n', 'w', 'e', 'n']
    >>> 
    
    3  通过range() 创建整数列表：
    range([start],[end],[step])
    注意：range 返回的是range对象，不是列表。需要用list（）方法将其转化成列表。
    例如：
    >>> list(range(3,15,2))
    [3, 5, 7, 9, 11, 13]
    >>> list(range(15,3,-1))
    [15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4]
    
    4 推导式生成列表：
    >>> a = [x*2 for x in range(5)]
    >>> a
    [0, 2, 4, 6, 8]
    >>> a = [x*2 for x in range(100) if x%9==0]
    >>> a
    [0, 18, 36, 54, 72, 90, 108, 126, 144, 162, 180, 198]
    
    p34
    
    1列表元素的增加和删除：
    append()方法：
    >>> a = [20,30]
    >>> a.append(40)
    >>> a
    [20, 30, 40]
    
    +：
    >>> a=[20,40]
    >>> id(a)
    69048720
    >>> a = a+[50]
    >>> a
    [20, 40, 50]
    >>> id(a)
    59868944
    注：两者的区别在于，后者的存储地址发生了改变。
    
    extend（）方法：
    >>> a = [20,40]
    >>> id(a)
    69048720
    >>> a.extend([50])
    >>> a
    [20, 40, 50]
    >>> id(a)
    69048720
    >>> 
    
    2 元素的插入：
    >>> a = [20,30,40,50]
    >>> a.insert(2,100)
    >>> a
    [20, 30, 100, 40, 50]
    >>> 
    
    3  乘法扩展：
    >>> a = ['sxt',100]
    >>> b = a*3
    >>> a
    ['sxt', 100]
    >>> b
    ['sxt', 100, 'sxt', 100, 'sxt', 100]
    >>> 
    
    p35:
    
    del删除：
    >>> a = [100,200,300]
    >>> del a[1]
    >>> a
    [100, 300]
    
    pop删除：
    >>> a = [10,20,30,40]
    >>> a.pop()
    40
    >>> a
    [10, 20, 30]
    >>> a.pop(0)
    10
    >>> a
    [20, 30]
    >>> 
    
    remove ：删除首次出现的元素：
    >>> a = [10,20,10,30,10,40]
    >>> a.remove(10)
    >>> a
    [20, 10, 30, 10, 40]
    >>> 
    
    p36
    
    列表元素的访问和计数：
    index（）获取指定元素首次出现的时候的索引：
    格式： index(值，[start],[end])
    >>> a = [10,20,30,40,50,60]
    >>> a.index(30,2)
    2
    >>> a.index(30,3)
    Traceback (most recent call last):
      File "<pyshell#59>", line 1, in <module>
        a.index(30,3)
    ValueError: 30 is not in list
    >>> a.index(30,-1)
    Traceback (most recent call last):
      File "<pyshell#60>", line 1, in <module>
        a.index(30,-1)
    ValueError: 30 is not in list
    >>> a.index(30,0,2)
    Traceback (most recent call last):
      File "<pyshell#61>", line 1, in <module>
        a.index(30,0,2)
    ValueError: 30 is not in list
    >>> a.index(30,0,4)
    2
    >>> 
    
    count() :获得次数：
    >>> a = [10,10,10,20,10]
    >>> a.count()
    Traceback (most recent call last):
      File "<pyshell#65>", line 1, in <module>
        a.count()
    TypeError: count() takes exactly one argument (0 given)
    >>> a.count(10)
    4
    
    
    len()：获取长度：
    >>> 
    >>> a = [10,10,10,20,10]
    >>> len(a)
    5
    
    
    判断元素是否存在？？
    >>> a = [10,20,39,49]
    >>> 10 in a
    True
    >>> 30 in a
    False
    >>> 
    
    p37:
    
    切片操作：
    >>> a = [10,20,30,40,50,60]
    >>> a[:]
    [10, 20, 30, 40, 50, 60]
    >>> a[1:3:1]
    [20, 30]
    >>> a[1:5:2]
    [20, 40]
    >>> 
    
    列表的遍历：
    >>> a = [1,2,3,4,5,6,2]
    >>> for x in a:
    	print(x)	
    1
    2
    3
    4
    5
    6
    2
    >>> 
    
    
    复制列表的所有信息：
    >>> list1 = [1,2,3,4]
    >>> list2 = list1
    >>> list2
    [1, 2, 3, 4]
    >>> 
    
    p38:
    
    列表排序：
    
    1.修改原列表，不生成新列表：
    >>> a = [3,2,4,5,1]
    >>> a.sort()
    >>> a
    [1, 2, 3, 4, 5]
    >>> a.sort(reverse=True)
    >>> a
    [5, 4, 3, 2, 1]
    >>> 
    
    2.建立新列表排序：
    
    >>> a = [2,3,1,4,2,5]
    >>> a = sorted(a)
    >>> a
    [1, 2, 2, 3, 4, 5]
    >>> a = sorted(a,reverse=True)
    >>> a
    [5, 4, 3, 2, 2, 1]
    >>> 
    
    reverse（）迭代器的用法：
    >>> a = [20,10,30,40]
    >>> a[::-1]
    [40, 30, 10, 20]
    >>> a = reversed(a)
    >>> a
    <list_reverseiterator object at 0x03598690>
    >>> list(a)
    [40, 30, 10, 20]
    >>> 
    
    
    max  min  返回最大值和最小值：
    sum 求和：
    >>> a = [10,20,3,40,60]
    >>> min(a)
    3
    >>> max(a)
    60
    >>> sum(a)
    133
    
    p39
    
    
    二维数组：：
    
    >>> a=[
    	[1,2,3],
    	[4,5,6],
    	[7,8,9],
          ]
    >>> a
    [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
    >>> a[1][2]
    6