读取文件- python？

Question

我想使用split string方法将每一行的信息提取到一个列表中。

Answer 1

使用拆分线，这样会更好：

file = open('scores.txt','r').read().splitlines()
exam_one = []
for line in file:
    line = line.split() # not strip
    exam_one.append(int(line[2])) # or better use float() since it's an exam
print(exam_one) # => [100, 82, 94, 89, 87]

Answer 2

我不知道你的档案是怎样的，但我认为它是这样的：

Hopper, Grace 100 98 87 97
Knuth, Donald 82 87 92 81
Goldberg, Adele 94 96 90 91
Kernighan, Brian 89 74 89 77
Liskov, Barbara 87 97 81 85

我也不明白你想要什么样的输出，但我认为是这样的：

[['Hopper,', 'Grace', '100', '98', '87', '97'], ['Knuth,', 'Donald', '82', '87', '92', '81'], ['Goldberg,', 'Adele', '94', '96', '90', '91'], ['Kernighan,', 'Brian', '89', '74', '89', '77'], ['Liskov,', 'Barbara', '87', '97', '81', '85']]

我已经开发了这一行代码(适用于 3.6):

with open('scores.txt', 'r') as file:
    print([[value for value in line.strip().replace(',','').split()] for line in file])

与：相同

with open('scores.txt', 'r') as file:
    tmp = []
    for line in file:
        tmp.append(line.strip().replace(',','').split())
        # Also you can delete tmp = [] and replace the tmp.append(...) line to tmp = [var for var in line.strip().replace(',','').split()]
print(tmp)

输出：

[['Hopper,', 'Grace', '100', '98', '87', '97'], ['Knuth,', 'Donald', '82', '87', '92', '81'], ['Goldberg,', 'Adele', '94', '96', '90', '91'], ['Kernighan,', 'Brian', '89', '74', '89', '77'], ['Liskov,', 'Barbara', '87', '97', '81', '85']]

与：相同

[
    ['Hopper,', 'Grace', '100', '98', '87', '97'],
    ['Knuth,', 'Donald', '82', '87', '92', '81'],
    ['Goldberg,', 'Adele', '94', '96', '90', '91'],
    ['Kernighan,', 'Brian', '89', '74', '89', '77'],
    ['Liskov,', 'Barbara', '87', '97', '81', '85']
]

我使用了like和output print()，但您可以根据需要定义变量。

PD:我找到了一个更简单的解决方案：

with open('scores.txt', 'r') as file:
    print([line.split() for line in file.read().replace(',','').splitlines()])

Answer 3

假设您有以下字符串，其中包含单词(由水平空格分隔)和行(由\n或垂直空格分隔)：

>>> print(data)
Hopper, Grace 100 98 87 97
Knuth, Donald 82 87 92 81
Goldberg, Adele 94 96 90 91
Kernighan, Brian 89 74 89 77
Liskov, Barbara 87 97 81 85

如果你仅仅使用.split()，你就失去了行和词之间的所有区别：

>>> data.split()
['Hopper,', 'Grace', '100', '98', '87', '97', 'Knuth,', 'Donald', '82', '87', '92', '81', 'Goldberg,', 'Adele', '94', '96', '90', '91', 'Kernighan,', 'Brian', '89', '74', '89', '77', 'Liskov,', 'Barbara', '87', '97', '81', '85']

为了保持这种差异，您需要将.splitlines()与.split()结合使用

>>> [line.split() for line in data.splitlines()]
[['Hopper,', 'Grace', '100', '98', '87', '97'], ['Knuth,', 'Donald', '82', '87', '92', '81'], ['Goldberg,', 'Adele', '94', '96', '90', '91'], ['Kernighan,', 'Brian', '89', '74', '89', '77'], ['Liskov,', 'Barbara', '87', '97', '81', '85']]

同样的概念也适用于从文件读取的数据。您可以使用for循环遍历文件的各个行，而不是使用.splitlines()：

>>> with open('/tmp/file.txt') as f:
...    for line in f:
...       print(line.split())
... 
['Hopper,', 'Grace', '100', '98', '87', '97']
['Knuth,', 'Donald', '82', '87', '92', '81']
['Goldberg,', 'Adele', '94', '96', '90', '91']
['Kernighan,', 'Brian', '89', '74', '89', '77']
['Liskov,', 'Barbara', '87', '97', '81', '85']

或者，如果您想要嵌套列表：

>>> with open('/tmp/file.txt') as f:
...    print([line.split() for line in f])
... 
[['Hopper,', 'Grace', '100', '98', '87', '97'], ['Knuth,', 'Donald', '82', '87', '92', '81'], ['Goldberg,', 'Adele', '94', '96', '90', '91'], ['Kernighan,', 'Brian', '89', '74', '89', '77'], ['Liskov,', 'Barbara', '87', '97', '81', '85']]

如果您只想要这些行中的一个数字：

>>> with open('/tmp/file.txt') as f:
...    print([line.split()[2] for line in f])
... 
['100', '82', '94', '89', '87']

使用Python循环或列表理解打开文件并遍历各行的形式被认为是一种重要的for习惯用法。使用它们，而不是将整个文件读取到内存中。