Python在不使用regex的情况下替换整个单词

Question

我想在不使用regex的情况下用另一个字符串替换整个单词。replace_all_whole_words1可以实现我想要的功能，但我不想使用regex，并且只用于测试我的replace_all_whole_words2函数是否正常工作(它不是(。

import re
def replace_all_whole_words1(needle, replacement, haystack):
needle = re.escape(needle)
return re.sub(r"b%sb" % needle, replacement, haystack)
def replace_all_whole_words2(needle, replacement, haystack):
i=0
while len(haystack) > i:
found_word = False
found_word_start = i
found_word_end = 0
found_type = 0 # will repersent if we found,  word + " " or " " + word or " " + word + " " ()
if i == 0:
found_word = haystack[i:i+len(needle + " " )] == needle + " "
found_word_end = i + len(needle) 
found_type = 1
elif i == len(haystack) - len(" " + needle):
found_word = haystack[i:i+len(" " + needle)] == " " + needle
found_word_end = i + len(" " + needle)
found_type = 2
else:
found_word = haystack[i:i+len(" "  + needle + " " )] == " "  + needle + " "
found_word_end = i + len(" " + needle + " ")
found_type = 3
if found_word:
print(haystack, found_word_start, found_word_end, i, found_type)
haystack = haystack[:found_word_start] + replacement + haystack[found_word_end:]
i += 1
return haystack

needle = "test"
replacement = "replaced"
haystack = "test test test testa atest"
print(
replace_all_whole_words1(needle, replacement, haystack) == replace_all_whole_words2(needle, replacement, haystack)
)
print(
replace_all_whole_words2(needle, replacement, haystack)
)

Answer 1

这里已经有几个很棒、更简单的答案，将haystack转换为列表，执行替换，然后将其转换回字符串。如果你仍然想在整个过程中使用草垛作为字符串，请查看我制作的这个解决方案。

def replace_all_whole_words2(needle, replacement, haystack):
# Counter to go through characters in haystack
i = 0 

# This will collect all chars separated by space as word
word = '' 

# len_needle will control replacement insertion and diff will adjust i after insertion 
len_needle = len(needle)
diff = len(replacement) - len_needle

# Go through characters in haystack and replace needle with replacement
while i < len(haystack):
char = haystack[i]
if char == ' ':
if word == needle:
haystack = haystack[:(i-len_needle)] + replacement + haystack[i:]

# Adjust i so that you can continue from the next char after the space
i += diff

# Reset word to collect new chars
word = ''
else:
word += char

i += 1

return haystack

测试：

needle = "test"
replacement = "replacement"
haystack = "test test test testa atest"
replace_all_whole_words2(needle, replacement, haystack)

输出：

'replacement replacement replacement testa atest'

Answer 2

为什么不转换为列表？因为你只是在删除单词。

def replace_all_whole_words2(needle, replacement, haystack):
l = haystack.split()
for idx, word in enumerate(l):
if word == needle:
l[idx] = replacement
return ' '.join(l)

Answer 3

如注释中所述，用split分隔，使用列表理解，然后重新加入：

def replace_all_whole_words2(needle, replacement, haystack):
word_list = haystack.split(' ')
new_list = [replacement if word == needle else word for 
word in word_list]
return " ".join(new_list)