Unexpected outcome, manipulating string on Python

Question

I am writing some code in Python, trying to clean a string all to lower case without special characters.

string_salada_russa = '    !!   LeTRas PeqUEnAS &    GraNdeS'

clean_string = string_salada_russa.lower().strip()


print(clean_string)

i = 0

for c in clean_string:
  if(c.isalpha() == False and c != " "):
    clean_string = clean_string.replace(c, "").strip()


print(clean_string)

for c in clean_string:
  if(i >= 1 and i <= len(clean_string)-1):
    if(clean_string[i] == " " and clean_string[i-1] == " " and clean_string[i+1] == " "):
      clean_string = clean_string.replace(clean_string[i], "")
  i += 1


  
print(clean_string)

Expected outcome would be:

#original string
'    !!   LeTRas PeqUEnAS &    GraNdeS'

#expected
'letras pequenas grandes'

#actual outcome
'letraspequenasgrandes'

I am trying to remove the extra spaces, however unsucessfully. I end up removing ALL spaces.

Could anyone help me figure it out? What is wrong in my code?

This is probably because you shorten clean_string while iterating over it. A better strategy might be to iterate over clean_string and copy the letters you want to keep to another string (or even better, to a list, which you then join together when you're done). — Matthias Fripp
– Matthias Fripp, Commented Nov 1, 2021 at 0:45

j1-lee · Accepted Answer · 2021-11-01 00:40:55Z

2

How about using re?

import re

s = '    !!   LeTRas PeqUEnAS &    GraNdeS'
s = re.sub(r"[^a-zA-Z]+", " ", s.lower()).strip()
print(s) # letras pequenas grandes

This first translates the letters into lower case (lower), replace each run of non-alphabetical characters into a single blank (re.sub), and then remove blanks around the string (strip).

Btw, your code does not output 'letraspequenasgrandes'. Instead, it outputs 'letrasZpequenasZZZZZgrandes'.

answered Nov 1, 2021 at 0:40

j1-lee

13.9k3 gold badges16 silver badges27 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

norok2 · Accepted Answer · 2021-11-01 00:49:28Z

2

You could get away with a combination of str.lower(), str.split(), str.join() and str.isalpha():

def clean(s):
    return ' '.join(x for x in s.lower().split(' ') if x.isalpha())


s = '    !!   LeTRas PeqUEnAS &    GraNdeS'
print(clean(s))
# letras pequenas grandes

Basically, you first convert to lower and the split by ' '. After that you filter out non-alpha tokens and join them back.

answered Nov 1, 2021 at 0:49

norok2

27.1k6 gold badges83 silver badges110 bronze badges

Comments

score 1 · Accepted Answer · 2021-11-01 17:21:46Z

1

There's no need to strip your string at each iteration of the first for loop; but, other than that, you could keep the first piece of your code:

for c in clean_string:
    if (c.isalpha() == False and c != " "):
        clean_string = clean_string.replace(c, "")

Then split your string, effectively removing all the spaces, and re-join the word back into a single string, with a single space between each word:

clean_string = " ".join(clean_string.split())

edited Nov 1, 2021 at 17:21

answered Nov 1, 2021 at 1:38

user16845332

1 Comment

norok2 Over a year ago

Do note that this will be somewhat inefficient, since the whole string will be copied at each iteration when there is an invalid char.

Collectives™ on Stack Overflow

Unexpected outcome, manipulating string on Python

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related