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!

你可以在python中使用sed、awk或grep(有一些限制)。这里有一个非常简单的例子。它在文件中把香蕉变成香蕉牙膏。你可以编辑和使用它。(我测试过了…注意:如果你在Windows下测试，你应该先安装sed命令并设置路径)

import os 
file="a.txt"
oldtext="Banana"
newtext=" BananaToothpaste"
os.system('sed -i "s/{}/{}/g" {}'.format(oldtext,newtext,file))
#print(f'sed -i "s/{oldtext}/{newtext}/g" {file}')
print('This command was applied:  sed -i "s/{}/{}/g" {}'.format(oldtext,newtext,file))

如果你想直接在文件上看到结果，应用:"type" for windows/ "cat" for linux:

####FOR WINDOWS:
os.popen("type " + file).read()
####FOR LINUX:
os.popen("cat " + file).read()

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()

我也有同样的问题。问题是，当你在变量中加载一个.txt时，你把它当作一个字符串数组使用，而它是一个字符数组。

swapString = []
with open(filepath) as f: 
    s = f.read()
for each in s:
    swapString.append(str(each).replace('this','that'))
s = swapString
print(s)

def word_replace(filename,old,new):
    c=0
    with open(filename,'r+',encoding ='utf-8') as f:
        a=f.read()
        b=a.split()
        for i in range(0,len(b)):
            if b[i]==old:
                c=c+1
        old=old.center(len(old)+2)
        new=new.center(len(new)+2)
        d=a.replace(old,new,c)
        f.truncate(0)
        f.seek(0)
        f.write(d)
    print('All words have been replaced!!!')

我试过用readline代替read

with open('dummy.txt','r') as file:
    list = file.readlines()
print(f'before removal {list}')
for i in list[:]:
        list.remove(i)

print(f'After removal {list}')
with open('dummy.txt','w+') as f:
    for i in list:
        f.write(i)