在Python中搜索并替换文件中的一行

Question

我想遍历文本文件的内容，进行搜索并替换某些行，然后将结果写回到文件中。我可以先将整个文件加载到内存中，然后再写回去，但这可能不是最好的方法。

在以下代码中，执行此操作的最佳方法是什么？

f = open(file)
for line in f:
    if line.contains('foo'):
        newline = line.replace('foo', 'bar')
        # how to write this newline back to the file

Answer 1

我想类似的事情应该做。它基本上将内容写入新文件，并用新文件替换旧文件：

from tempfile import mkstemp
from shutil import move, copymode
from os import fdopen, remove

def replace(file_path, pattern, subst):
    #Create temp file
    fh, abs_path = mkstemp()
    with fdopen(fh,'w') as new_file:
        with open(file_path) as old_file:
            for line in old_file:
                new_file.write(line.replace(pattern, subst))
    #Copy the file permissions from the old file to the new file
    copymode(file_path, abs_path)
    #Remove original file
    remove(file_path)
    #Move new file
    move(abs_path, file_path)