CODEWITHSUNDEEP
python
Yolanda
Yolanda

Reputation: 27

implement my own strip method in Python

I am trying to implement my own strip method in Python, so without using the built-in method, I'd like my function to strip out all the whitespace from the left and the right.

Here, what I am trying to do is create a list, remove all the blank character before the first non-space character, then do it reverse way, finally return the list to a string. But with what I wrote, it doesn't even remove one whitespace.

I know what I am trying to do might not even work, so I would also like to see the best way to do this. I am really new to programming, so I would take any piece of advise that makes my program better. Thanks!

# main function
inputString = input("Enter here: ")
print(my_strip(inputString))

def my_strip(inputString):
    newString = []
    for ch in inputString:
        newString.append(ch)
    print(newString)
    i = 0
    while i < len(newString):
        if i == " ":
            del newString[i]
        elif i != " ":
            return newString
        i += 1
    print(newString)

Upvotes: 1

Views: 2165

Answers (3)

user1952500
user1952500

Reputation: 6771

What you seem to be doing is an ltrim for spaces, since you return from the function when you get a non-space character.

Some changes are needed:

# main function
inputString = input("Enter here: ")
print(my_strip(inputString))

def my_strip(inputString):
    newString = []
    for ch in inputString:
        newString.append(ch)
    print(newString)
    i = 0
    while i < len(newString):
        if i == " ": # <== this should be newString[i] == " "
            del newString[i]
        elif i != " ": # <== this should be newString[i] == " "
            return newString
        i += 1 # <== this is not needed as the char is deleted, so the next char has the same index
    print(newString)

So the updated code will be:

# main function
inputString = input("Enter here: ")
print(my_strip(inputString))

def my_strip(inputString):
    newString = []
    for ch in inputString:
        newString.append(ch)
    print(newString)
    i = 0
    while i < len(newString):
        if newString[i] == " ":
            del newString[i]
        elif newString[i] != " ":
            return newString
    print(newString)

Good luck with the rest of the exercise (implementation of rtrim).

Upvotes: 0

Enix
Enix

Reputation: 4579

How about using regular expression?

import re

def my_strip(s):
   return re.sub(r'\s+$', '', re.sub(r'^\s+', '', s))

>>> my_strip('   a c d    ')
'a c d'

Upvotes: 0

Patrick Haugh
Patrick Haugh

Reputation: 61014

Instead of doing a bunch of string operations, let's just get the beginning and ending indices of the non-whitespace portion and return a string slice.

def strip_2(s):
    start = 0
    end = -1
    while s[start].isspace():
        start += 1
    while s[end].isspace():
        end -= 1
    end += 1
    return s[start:end or None]

Upvotes: 4

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