Member Avatar for bf2loser

I have to strip anything that isn't a letter between a-z (lowercase only) out of a sentence. I wrote this

def breakPhrase(string):
    string=string.lower()
    for character in string:
        if ord(character) < 97 or ord(character) > 122:
            string=string.strip(character)
    return string

and it works, but only if theres only one punctuation or non alphabetical character. like if I passed "i dont know..." it would only strip out one of the periods, where I need it to strip all of them out. what am I doing wrong?

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  • Latest Post Latest Post by sachin004

Dani AI

Generated

Good catch from : str.strip() only trims the ends, so calling it inside a loop will never touch punctuation in the middle of the string. Also, rebinding string while iterating still walks the original characters, which makes the behavior even less intuitive.

If you truly want to allow only a-z (lowercase) and drop everything else, build a new string instead of mutating. This avoids quadratic concatenation and is easy to reason about:

def only_a_to_z(s):
    s = s.lower()
    return ''.join(ch for ch in s if 'a' <= ch <= 'z')

If your assignment expects spaces to survive (so words remain readable), allow a space explicitly:

def only_a_to_z_with_spaces(s):
    s = s.lower()
    return ''.join(ch for ch in s if ('a' <= ch <= 'z') or ch == ' ')

A regex alternative is concise and fast for large inputs. It deletes anything not in your allowed set:

import re

def keep_only_a_to_z(s, keep_spaces=False):
    s = s.lower()
    return re.sub(r'[^a-z ]+' if keep_spaces else r'[^a-z]+', '', s)

Notes:

  • @kdoiron is right about avoiding raw ASCII codes; comparing characters or using a whitelist is clearer and portable.
  • ’s \w matches letters, digits, and underscore. If you need strictly a-z, prefer [a-z] (and [a-z ] if keeping spaces).
  • Favor ''.join(...) or re.sub(...) over concatenating in a loop for better performance.

Recommended Answers

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Member Avatar for Lardmeister

The strip() function only removes leading and trailing characters:

text = 'goodbye! cruel, harsh world!..?'
print text.strip('!,.?')  # goodbye! cruel, harsh world

To remove characters all through the text you can use a loop this way:

text = 'goodbye! cruel, harsh world!..?!'
stripped_text = ""
for c in text:
    if c in '!,.?':
        c = ""
    stripped_text += c

print stripped_text  # goodbye cruel harsh world
Member Avatar for bf2loser

Ahh I see, now that you say that I kinda remember reading that about the strip function, well with that I should be able to get this working easily, thank you!

Member Avatar for Member #322302

Use the string module - it has a built-in for lower-case letters. This is preferable to specifying the ASCII characters - what happens if you run on an EBCDIC system? You're better off seeing if each character is valid, and if it is, appending it to a new string.

Member Avatar for bf2loser

I'll keep that in mind, I don't think its important for this assignment since it isn't going to be used in any real world application, its just an assignment. But thanks for the info, I'll check it out a later tonight

Member Avatar for sachin004 
import re
a="what is. your. name?"
b=re.findall(r'\w+',a)
print b
#this program removes all punctuation and prints the final output
Edited by peter_budo because: Keep It Clear - Please use code tags
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