python - 将字符串列表从文件转换为整数列表

Question

我有一个大文件，其中充满了由空格和逗号分隔的整数。我试图一次读取 1KB 数据并将其转换为整数列表。

这段代码工作正常:

with open('test_age.txt', 'r+') as inf:
    with open('test_age_out.txt', 'r+') as outf:
        sorted_list =[]
        a = [x.strip() for x in inf.read(1000).split(',')]
        int_a = map(int, a)
        f = tempfile.TemporaryFile()
        outf_array = sorted(int_a)
        f.write(str(outf_array))
        f.seek(0)
        #etc...

输出:

[1, 1, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, etc...

但是一旦我添加 while 循环来读取下一个 1KB:

with open('test_age.txt', 'r+') as inf:
    with open('test_age_out.txt', 'r+') as outf:
        sorted_list =[]
        while True:
            a = [x.strip() for x in inf.read(1000).split(',')]
            int_a = map(int, a)
            if not a:
                break
            f = tempfile.TemporaryFile()
            outf_array = sorted(int_a)
            print outf_array
            f.write(str(outf_array))
            f.seek(0)      

我得到输出和 ValueError:

[1, 1, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 
8, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 12, 12, 12,
12, 12, 12, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 15, 15, 16, 17, 18,
19, 19, 20, 20, 20, 20, 21, 21, 22, 22, 22, 23, 23, 24, 24, 24, 24, 25, 
25, 25, 25, 25, 26, 26, 26, 26, 27, 27, 27, 28, 28, 29, 30, 30, 30, 30,
31, 31, 31, 32, 32, 33, 33, 33, 33, 33, 33, 34, 34, 34, 34, 34, 35, 35,
35, 35, 35, 36, 36, 37, 37, 37, 37, 38, 38, 39, 39, 39, 39, 39, 39, 40,
40, 40, 40, 41, 41, 42, 43, 43, 43, 44, 44, 44, 44, 44, 45, 46, 46, 46,
46, 47, 47, 47, 47, 47, 48, 48, 48, 48, 48, 48, 49, 49, 49, 50, 50, 50,
50, 50, 50, 51, 51, 51, 51, 51, 51, 52, 52, 52, 52, 52, 52, 53, 53, 54,
54, 54, 55, 55, 55, 55, 56, 56, 56, 56, 56, 57, 57, 57, 57, 58, 58, 58,
59, 59, 60, 60, 60, 61, 62, 62, 62, 62, 63, 63, 63, 63, 63, 63, 63, 64,
64, 64, 65, 66, 66, 67, 67, 67, 67, 68, 68, 68, 68, 68, 69, 69, 69, 69, 
69, 69, 69, 70, 70, 70, 70, 71, 71, 72, 72, 73, 74, 74, 74, 75, 76, 76,
76, 76, 77, 77, 77, 77, 78, 78, 79, 79, 79, 79, 81, 81, 81, 81, 82, 82, 
82, 82, 82, 83, 83, 83, 83, 84, 85, 85, 85, 85, 86, 86, 86, 87, 87, 87,
87, 87, 87, 88, 88, 88, 88, 88, 88, 88, 89, 89, 89, 89, 90, 90, 90, 91,
91, 91, 91, 91, 91, 91, 92, 92, 93, 93, 93, 94, 94, 94, 94, 95,  95,
96, 96, 96, 97, 97, 98, 99, 100, 100, 100, 100, 100]
[2, 3, 3, 3, 3, 4, 4, 5, 5, 6, 8, 9, 10, 10, 11, 11, 11, 11, 12, 12,12, 
13, 14, 15, 17, 17, 17, 17, 17, 17, 18, 18, 18, 20, 21, 22, 22, 22, 22, 
23, 23, 24, 24, 24, 26, 27, 27, 27, 27, 28, 28, 29, 29, 29, 29, 30, 32, 
32, 32, 32, 33, 33, 34, 34, 36, 37, 37, 37, 37, 38, 39, 41, 41, 42, 43,   
44, 44, 46, 46, 47, 48, 49, 49, 49, 49, 51, 51, 52, 52, 52, 52, 53, 54, 
54, 54, 55, 55, 56, 60, 60, 61, 61, 61, 62, 63, 63, 64, 65, 65, 65, 65, 
66, 66, 67, 68, 68, 68, 70, 70, 73, 73, 73, 74, 74, 75, 75, 75, 77, 77, 
77, 77, 78, 78, 78, 78, 79, 80, 81, 81, 82, 82, 83, 83, 83, 83, 84, 84, 
85, 85, 85, 85, 86, 87, 88, 90, 91, 91, 91, 92, 93, 93, 93, 94, 95, 97, 
98, 98, 99, 100]
    int_a = map(int, a)
ValueError: invalid literal for int() with base 10: ''

我不确定为什么会发生这种情况。如果我调用 print，似乎列表正在被创建和排序。但是 ValueError 存在。给出了什么？

Answer 1

查看 str.split 的输出，其中传递的分隔符出现在字符串的头部或尾部:

>>> ', 3, 5'.split(', ')
['', '3', '5']

该空字符串是您的程序尝试(但失败)解析为整数的内容。 ''.strip() 没有帮助(顺便说一句，对于 int() 来说也不是必需的 - 它会自动忽略前导和尾随空格)。我建议阅读保证完整且有效的 block ，例如行。如果文件只是一大行，您将必须做一些额外的工作来保存一行中的最后一个字符并将它们移动到下一行的处理中。不要忘记在循环后处理剩余的字符。

line = inf.read(1000)
new += line
current, delimiter, new = line.rpartition(', ')
# process current
# continue loop to add more content

如果该文件可以轻松地放入您的系统内存中，您可以读取整个文件并将其一次性拆分:

numbers = map(int, inf.read().split(', '))