现有文件testdata.csv内容如下：

    1. name,C,Java,Python,C#,C++,id
    2. Rome,-95,96,85,63,91,826
    3. Juja,75,93,66,85,88,8984
    4. Lisi,86,76,100,93,67,10566
    5. Zhengj,-88,96,9,90,89,10588
    6. Wangx,99,96,91,88,86,10896

    读取其中数据并转为二维列表：

    1. ls = []                                                  #  创建空列表备
    2. with open('testdata.csv','r',encoding='utf-8') as data:  # 读文件，创建文件对象
    3.     for line in data:                                    # 遍历文件对象data，每次得到其一行，格式为字符串
    4.         print(line)                                      # 'Rome,-95,96,85,63,91,826\n'
    5.         ls.append(line.strip().split(','))               # 文件的一行切分为元素为符串的列表加入列表中
    6. print(ls)

    输出结果为：
    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’]]

    上述功能可以用列表推导式实现，代码如下：

    1. with open('testdata.csv','r',encoding='utf-8') as data:  # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]

    尝试直接对其排序输出，使用sorted()函数实现：

    1. with open('testdata.csv','r',encoding='utf-8') as data:  # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print(sorted(ls))

    发现结果是按 ls 元素的第一个子元素的字母表顺序进行排序输出：
    [[‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’],
    [‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’]]

    此时标题行参与了排序，明显不符合要求，可以将第一行先切下来，排序后再拼接到一起：

    1. with open('testdata.csv','r',encoding='utf-8') as data:  # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:]))    # 将序号为 0 的元素切下来，对剩下元素进行排序，再拼接为一个新列表输出

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’]]

    如果题目要求排序关键字不是第一个子元素时，例如要求按python成绩进行排序时，可以用lambda表达式实现。

    1. with open('testdata.csv','r',encoding='utf-8') as data:  # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:],key=lambda x:x[3]))        # 根据序号为 3 的元素值排序

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’]]

    此时注意列表中的课程成绩仍是字符串，排序时按字符串排序的结果是 ASCII 表的顺序，排序时应转为整数。从输出的可以看出，数据类型的转换并没有真实发生，只是在排序的时候按字符串对应的整数进行排序。

    1. with open('testdata.csv','r',encoding='utf-8') as data:   # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:],key=lambda x:int(x[3])))    # 字符串转整型参与排序

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’]]
    按python成绩降序排列：

    1. with open('testdata.csv','r',encoding='utf-8') as data:   # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:],key=lambda x:int(x[3]),reverse=True))    # 字符串转整型参与排序，降序排序

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’]]

    类似，可以要求按 C 语言成绩进行排序：

    1. with open('testdata.csv','r',encoding='utf-8') as data:   # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:],key=lambda x:int(x[1])))    # 字符串转整型参与排序

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’]]

    按 C 语言成绩的绝对值进行排序：

    1. with open('testdata.csv','r',encoding='utf-8') as data:     # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:],key=lambda x:abs(int(x[1])))) # 字符串转整型再取绝对值后参与排序

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],6
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’]]
    从结果中可以看出，在排序的时候，将每个值转为其绝对值进行比较排序，输出时，还是输出该元素实际存储的数值。

    根据 id 值进行排序，id是一个序号，可以按字符串排序：

    1. with open('testdata.csv','r',encoding='utf-8') as data:     # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:],key=lambda x:x[6]))           # 根据 id排序

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’]]
    根据 id 长度进行排序：

    1. with open('testdata.csv','r',encoding='utf-8') as data:     # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:],key=lambda x:len(x[6])))           # 根据 id 长度排序

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’]]

    可以同时按多个元素进行排序，按主次关系排序构建一个元组共同做为排序关键字，下面按C语言成绩升序排序，C语言成绩相同时，按ptyhon成绩升序排序。由元组 (int(x[2]),int(x[3])))作为排序关键字。

    1. with open('testdata.csv','r',encoding='utf-8') as data:  # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:],key=lambda x:(int(x[2]),int(x[3]))))    # 将序号为2 的排序，该值相同时按序号为3的元素排序

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’]]

    下面按C语言成绩升序排序，C语言成绩相同时，按ptyhon成绩降序排序。因成绩为数值类型，可以转换一下思路，排序时 以 -int(x[3]) 为排序依据，按 -int(x[3]) 升序排序时，实际上是按 int(x[3]) 降序排序。所以可以由元组 (int(x[2]),-int(x[3])))作为排序关键字，使两个关键字可以按相同的规则同时升序或降序排序。

    1. with open('testdata.csv','r',encoding='utf-8') as data:  # 读文件，创建文件对象
    2.     ls = [line.strip().split(',') for line in data]
    3. print([ls[0]] + sorted(ls[1:],key=lambda x:(int(x[2]),-int(x[3]))))    # 将序号为 2 升序，该值相同时按序号为3的元素降序

    [[‘name’, ‘C’, ‘Java’, ‘Python’, ‘C#’, ‘C++’, ‘id’],
    [‘Lisi’, ‘86’, ‘76’, ‘100’, ‘93’, ‘67’, ‘10566’],
    [‘Juja’, ‘75’, ‘93’, ‘66’, ‘85’, ‘88’, ‘8984’],
    [‘Wangx’, ‘99’, ‘96’, ‘91’, ‘88’, ‘86’, ‘10896’],
    [‘Rome’, ‘-95’, ‘96’, ‘85’, ‘63’, ‘91’, ‘826’],
    [‘Zhengj’, ‘-88’, ‘96’, ‘9’, ‘90’, ‘89’, ‘10588’]]