CODEWITHSUNDEEP
python
IcoSli
IcoSli

Reputation: 3

My code is incorrectly removing a strings from a larger string

"""
This code takes two strings and returns a copy of the first string with
all instances of the second string removed
"""
# This function removes the letter from the word in the event that the 
# word has the letter in it
def remove_all_from_string(word, letter):
    while letter in word:
        find_word = word.find(letter)
        word_length = len(word)
        if find_word == -1:
            continue
        else:
            word = word[:find_word] + word[find_word + word_length:] 
    return word
# This call of the function states the word and what letter will be
# removed from the word
print(remove_all_from_string("bananas", "an"))

This code is meant to remove a defined string from a larger define string. In this case the larger string is "bananas" and the smaller string which is removed is "an".

In this case the smaller string is removed multiple times. I believe I am very close to the solution of getting the correct output, but I need the code to output "bas". Instead, it outputs "ba".

The code is supposed to remove all instances of "an" and print whatever is left, however it does not do this. Any help is appreciated.

Upvotes: 0

Views: 160

Answers (3)

jsbueno
jsbueno

Reputation: 110476

The Python language has built-in utilities to do that in a single expression. The fact that you need to do that, indicates you are doing sme exercise to better understand coding, and that is important. (Hint: to do it in a single glob, just use the string replace method)

So, first thing - avoid using built-in tools that perform more than basic tasks - in this case, in your tentative code, you are using the string find method. It is powerful, but combining it to find and remove all occurrences of a sub-string is harder than doing so step by step.

So, what ou need is to have variables to annotate the state of your search, and your result. Variables are "free" - do not hesitate in creating as many, and updating then inside the proper if blocks to keep track of your solution.

In this case, you can start with a "position = 0", and increase this "0" until you are at the end of the parent string. You check the character at that position - if it does match the starting character of your substring, you update other variables indicating you are "inside a match", and start a new "position_at_substring" index - to track the "matchee". If at any point the character in the main string does not correspond to the character on the substring: not an occurrence, you bail out (and copy the skipped charactrs to your result -therefore you also have to accumulate all skipped characters in a "match_check" substring) .

Build your code with the simplest 'while', 'if' and variable updates - stick it all inside a function, so that whenever it works, you can reuse it at will with no effort, and you will have learned a lot.

Upvotes: 0

azro
azro

Reputation: 54168

Your word_length should be len(letter), and as the while ensures the inclusion, don't need to test the value of find_word

def remove_all_from_string(word, replacement):
    word_length = len(replacement)
    while replacement in word:
        find_word = word.find(replacement)
        word = word[:find_word] + word[find_word + word_length:]
    return word

Note that str.replace exists

def remove_all_from_string(word, replacement):
    return word.replace(replacement, "")

Upvotes: 1

Kyle K.
Kyle K.

Reputation: 21

You can simply use the .replace() function for python strings.

def remove_all_from_string(word, letter):
    word = word.replace(letter, "")
    return word

print(remove_all_from_string("bananas", "an"))

Output: bas

Upvotes: 0

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