我想循环一个文本文件的内容，并在一些行上进行搜索和替换，并将结果写回文件。我可以先把整个文件加载到内存中，然后再把它写回来，但这可能不是最好的方法。
在下面的代码中，做到这一点的最佳方法是什么?
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
当前回答
下面是另一个经过测试的例子，它将匹配搜索和替换模式:
import fileinput
import sys
def replaceAll(file,searchExp,replaceExp):
for line in fileinput.input(file, inplace=1):
if searchExp in line:
line = line.replace(searchExp,replaceExp)
sys.stdout.write(line)
使用示例:
replaceAll("/fooBar.txt","Hello\sWorld!$","Goodbye\sWorld.")
其他回答
我想像这样的东西就可以了。它基本上将内容写入一个新文件，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)
如果您删除缩进如下所示，它将在多行中搜索和替换。 请看下面的例子。
def replace(file, pattern, subst):
#Create temp file
fh, abs_path = mkstemp()
print fh, abs_path
new_file = open(abs_path,'w')
old_file = open(file)
for line in old_file:
new_file.write(line.replace(pattern, subst))
#close temp file
new_file.close()
close(fh)
old_file.close()
#Remove original file
remove(file)
#Move new file
move(abs_path, file)
更python化的方法是使用上下文管理器，如下所示:
from tempfile import mkstemp
from shutil import move
from os import remove
def replace(source_file_path, pattern, substring):
fh, target_file_path = mkstemp()
with open(target_file_path, 'w') as target_file:
with open(source_file_path, 'r') as source_file:
for line in source_file:
target_file.write(line.replace(pattern, substring))
remove(source_file_path)
move(target_file_path, source_file_path)
你可以在这里找到完整的片段。
Fileinput非常简单，就像之前的答案中提到的那样:
import fileinput
def replace_in_file(file_path, search_text, new_text):
with fileinput.input(file_path, inplace=True) as file:
for line in file:
new_line = line.replace(search_text, new_text)
print(new_line, end='')
解释:
fileinput可以接受多个文件，但我更喜欢在处理每个文件时立即关闭它。因此，将单个file_path放在with语句中。 当inplace=True时，print语句不打印任何东西，因为STDOUT被转发到原始文件。 End = " in print语句是消除中间空白的新行。
你可以这样使用它:
file_path = '/path/to/my/file'
replace_in_file(file_path, 'old-text', 'new-text')
使用hamishmcn的答案作为模板，我能够在文件中搜索与我的正则表达式匹配的一行，并将其替换为空字符串。
import re
fin = open("in.txt", 'r') # in file
fout = open("out.txt", 'w') # out file
for line in fin:
p = re.compile('[-][0-9]*[.][0-9]*[,]|[-][0-9]*[,]') # pattern
newline = p.sub('',line) # replace matching strings with empty string
print newline
fout.write(newline)
fin.close()
fout.close()
