Python replace whole words without using regex-CodePudding

I am wanting to replace whole words with another string without using regex. The replace_all_whole_words1 does what I want, but I don't want to use regex and is only being used to test if my replace_all_whole_words2 function is working correctly (it isn't).

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)
)

CodePudding user response：

Why not convert to list? Since you are just deleting words.

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)

CodePudding user response：

As explained in the comments, separating with split, using list comprehension and then re joining:

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)