Python 不使用正则表达式替换整个单词

Question

我想在不使用正则表达式的情况下用另一个字符串替换整个单词。 replace_all_whole_words1 可以满足我的要求，但我不想使用正则表达式，它仅用于测试我的 replace_all_whole_words2 函数是否正常工作（不是）。

import re
def replace_all_whole_words1(needle, replacement, haystack):
    needle = re.escape(needle)
    return re.sub(r"\b%s\b" % 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

为什么不转换为列表？因为你只是删除单词。

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 2

正如评论中所解释的那样，用拆分分离，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)

Answer 3

这里已经有几个很棒且更简单的答案，可以将 haystack 转换为列表，执行替换，然后将其转换回字符串。如果您仍想始终将 haystack 用作字符串，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'

Python 不使用正则表达式替换整个单词

Python replace whole words without using regex

python

string

replace