Besides the answers already mentioned, here is an explanation of why you have some random characters at the end: You are opening the file in r+ mode, not w mode. The key difference is that w mode clears the contents of the file as soon as you open it, whereas r+ doesn't. This means that if your file content is "123456789" and you write "www" to it, you get "www456789". It overwrites the characters with the new input, but leaves any remaining input untouched. You can clear a section of the file contents by using truncate(<startPosition>), but you are probably best off saving the updated file content to a string first, then doing truncate(0) and writing it all at once. Or you can use my library :D

(pip install python-util)

from pyutil import filereplace

filereplace("somefile.txt","abcd","ram")

将所有出现的“abcd”替换为“ram”。 该函数还通过指定regex=True来支持regex

from pyutil import filereplace

filereplace("somefile.txt","\\w+","ram",regex=True)

免责声明:我是作者(https://github.com/MisterL2/python-util)

你可以这样做替换

f1 = open('file1.txt', 'r')
f2 = open('file2.txt', 'w')
for line in f1:
    f2.write(line.replace('old_text', 'new_text'))
f1.close()
f2.close()

我稍微修改了Jayram Singh的帖子，以替换每一个'!'字符转换为一个数字，我想在每个实例中增加这个数字。我想这对那些想要修改每行出现不止一次的字符并且想要迭代的人可能会有帮助。希望这能帮助到别人。PS-我在编码方面很新，所以如果我的帖子在任何方面都不合适，我很抱歉，但这对我来说是有效的。

f1 = open('file1.txt', 'r')
f2 = open('file2.txt', 'w')
n = 1  

# if word=='!'replace w/ [n] & increment n; else append same word to     
# file2

for line in f1:
    for word in line:
        if word == '!':
            f2.write(word.replace('!', f'[{n}]'))
            n += 1
        else:
            f2.write(word)
f1.close()
f2.close()

你也可以使用pathlib。

from pathlib2 import Path
path = Path(file_to_search)
text = path.read_text()
text = text.replace(text_to_search, replacement_text)
path.write_text(text)

使用re.subn可以对替换过程进行更多的控制，例如将单词分成两行，区分大小写的匹配。此外，它返回匹配的数量，如果没有找到字符串，可以使用这些匹配来避免浪费资源。

import re

file = # path to file

# they can be also raw string and regex
textToSearch = r'Ha.*O' # here an example with a regex
textToReplace = 'hallo'

# read and replace
with open(file, 'r') as fd:
    # sample case-insensitive find-and-replace
    text, counter = re.subn(textToSearch, textToReplace, fd.read(), re.I)

# check if there is at least a  match
if counter > 0:
    # edit the file
    with open(file, 'w') as fd:
        fd.write(text)

# summary result
print(f'{counter} occurence of "{textToSearch}" were replaced with "{textToReplace}".')

一些正则表达式:

添加re.I标志，re.IGNORECASE的缩写形式，用于不区分大小写的匹配 对于多行替换re.subn(r'\n*'.join(textToSearch)， textToReplace, fd.read()))，取决于数据也'\n{，1}'。注意，在这种情况下，textToSearch必须是纯字符串，而不是正则表达式!