如何替换每个单词中第一次出现的字符？

Question

如何替换每个单词中第一次出现的字符？

说我有这个字符串：

hello @jon i am @@here or @@@there and want some@thing in '@here"
#     ^         ^^        ^^^                   ^          ^ 

我想删除@每个单词的第一个，以便我最终得到一个像这样的最终字符串：

hello jon i am @here or @@there and want something in 'here
#     ^        ^        ^^                   ^         ^

只是为了澄清，“@”字符在每个单词中总是一起出现，但可以在单词的开头或其他字符之间。

I managed to remove the "@" character if it occurs just once by using a variation of the regex I found in Delete substring when it occurs once, but not when twice in a row in python, which uses a negative lookahead and negative lookbehind:

@(?!@)(?<!@@)

See the output:

>>> s = "hello @jon i am @@here or @@@there and want some@thing in '@here"
>>> re.sub(r'@(?!@)(?<!@@)', '', s)
"hello jon i am @@here or @@@there and want something in 'here"

So the next step is to replace the "@" when it occurs more than once. This is easy by doing s.replace('@@', '@') to remove the "@" from wherever it occurs again.

However, I wonder: is there a way to do this replacement in one shot?

Answer 1

我会对以下模式进行正则表达式替换：

@(@*)

然后用第一个捕获组替换，它是所有连续的 @ 符号，减去一个。

这应该捕获@出现在每个单词开头的每个单词，无论是在字符串的开头、中间还是结尾的单词。

inp = "hello @jon i am @@here or @@@there and want some@thing in '@here"
out = re.sub(r"@(@*)", '\\1', inp)
print(out)

这打印：

hello jon i am @here or @@there and want something in 'here

Answer 2

replace('@', '', 1)在生成器表达式中使用怎么样？

string = 'hello @jon i am @@here or @@@there and want some@thing in "@here"'
result = ' '.join(s.replace('@', '', 1) for s in string.split(' '))

# output: hello jon i am @here or @@there and want something in "here"

的 int 值1是可选count参数。

str.replace(old, new[, count])

返回字符串的副本，其中所有出现的子字符串old 都被new替换。如果给出了可选参数 计数，则仅替换第一个计数出现。