如何在没有换行符的情况下读取文件? [英] How to read a file without newlines?

问题描述

在 Python 中，调用

In Python, calling

temp = open(filename,'r').readlines()

生成一个列表，其中每个元素都是文件中的一行.这有点愚蠢，但仍然: readlines() 还向每个元素写入换行符，这是我不希望发生的.

results in a list in which each element is a line in the file. It's a little stupid but still: readlines() also writes newline character to each element, something I do not wish to happen.

我怎样才能避免它?

推荐答案

您可以使用 str.splitlines:

You can read the whole file and split lines using str.splitlines:

temp = file.read().splitlines()

或者您可以手动去除换行符:

Or you can strip the newline by hand:

temp = [line[:-1] for line in file]

注意:最后一个解决方案仅适用于文件以换行符结尾的情况，否则最后一行将丢失一个字符.

Note: this last solution only works if the file ends with a newline, otherwise the last line will lose a character.

这个假设在大多数情况下都是正确的(特别是对于由文本编辑器创建的文件，无论如何它们通常会添加结束换行符).

This assumption is true in most cases (especially for files created by text editors, which often do add an ending newline anyway).

如果你想避免这种情况，你可以在文件末尾添加一个换行符:

If you want to avoid this you can add a newline at the end of file:

with open(the_file, 'r+') as f:
    f.seek(-1, 2)  # go at the end of the file
    if f.read(1) != '
':
        # add missing newline if not already present
        f.write('
')
        f.flush()
        f.seek(0)
    lines = [line[:-1] for line in f]

或者更简单的替代方法是 strip 换行:

Or a simpler alternative is to strip the newline instead:

[line.rstrip('
') for line in file]

甚至，虽然很难读:

[line[:-(line[-1] == '
') or len(line)+1] for line in file]

它利用了 or 的返回值不是布尔值，而是被评估为真或假的对象这一事实.

Which exploits the fact that the return value of or isn't a boolean, but the object that was evaluated true or false.

readlines 方法实际上相当于:

def readlines(self):
    lines = []
    for line in iter(self.readline, ''):
        lines.append(line)
    return lines

# or equivalently

def readlines(self):
    lines = []
    while True:
        line = self.readline()
        if not line:
            break
        lines.append(line)
    return lines

由于 readline() 保留了换行符，所以 readlines() 也保留了它.

Since readline() keeps the newline also readlines() keeps it.

注意:为了与 readlines() 对称，writelines() 方法不添加结束换行符，所以 f2.writelines(f.readlines()) 在 f2 中生成 f 的精确副本.

Note: for symmetry to readlines() the writelines() method does not add ending newlines, so f2.writelines(f.readlines()) produces an exact copy of f in f2.

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