CODEWITHSUNDEEP
python
user2191568
user2191568

Reputation: 41

replace letters in python string

Im writing a program for french that turns present tense verbs into past tense. The problem is that I need to replace letters but they are user inputed so I have to have it replacing the letters from the end of the line. Here's what I have so far, but it doesn't change the letters it just gives an error:

word = raw_input("what words do you want to turn into past tense?")
word2= word

if word2.endswith("re"):
 word3 = word2.replace('u', 're')
 print word3

elif word2.endswith("ir"):
 word2[-2:] = "i"
 print word2

elif word2.endswith("er"):
 word2[-2:] = "e"
 print word2

else:
 print "nope"

I tried word replace and that doesn't work either, it just gives me back the same string. If some one could just give me an example and maybe explain it a little that would be awesome. :/

Upvotes: 2

Views: 15696

Answers (5)

James Harvey
James Harvey

Reputation: 21

essentially what you've done wrong is "word2.replace('u', 're')" This means that you are replace 'u' with 're' inside the var word2. I have changed the code;

 word = raw_input("what words do you want to turn into past tense?")
 word2= word

 if word2.endswith("re"):
    word3 = word2.replace('re', 'u')
    print word3

  elif word2.endswith("ir"):
     word2[-2:] = "i"
     print word2

 elif word2.endswith("er"):
    word2[-2:] = "e"
    print word2

 else:
     print "nope"

Upvotes: 0

yoniLavi
yoniLavi

Reputation: 2752

I think that regular expressions will be a better solution here, and the subn method in particular.

import re

word = 'sentir'

for before, after in [(r're$','u'),(r'ir$','i'),(r'er$','e')]:
    changed_word, substitutions  = re.subn(before, after, word)
    if substitutions:
        print changed_word
        break
else:
    print "nope"

Upvotes: 0

ornoone
ornoone

Reputation: 651

String is inmutable, so u can't replace only the 2 last letters... you must create a new string from the existant.

and as said by MM-BB, replace will replace all the ocurance of the letter...

try

word = raw_input("what words do you want to turn into past tense?")
word2 = word

if word2.endswith("re"):
    word3 = word2[:-2] + 'u'
    print word3

elif word2.endswith("ir"):
    word3 = word2[:-2] + "i"
    print word3

elif word2.endswith("er"):
    word3 = word2[:-2] + "e"
    print word3

else:
    print "nope"

ex 1 :

what words do you want to turn into past tense?sentir
senti

ex 2 :

what words do you want to turn into past tense?manger
mange

Upvotes: 0

Mahdi-bagvand
Mahdi-bagvand

Reputation: 1407

excuse me

word3 = word2.replace('u', 're')

above line code can make a false result because
maybe exist another "er" in your word

Upvotes: 0

Anuvrat Parashar
Anuvrat Parashar

Reputation: 3120

IMO there might be a problem with the way you are using replace. The syntax for replace is explained. here

string.replace(s, old, new[, maxreplace])

This ipython session might be able to help you.

In [1]: mystring = "whatever"

In [2]: mystring.replace('er', 'u')
Out[2]: 'whatevu'

In [3]: mystring
Out[3]: 'whatever'

basically the pattern you want replaced comes first, followed by the string you want to replace with.

Upvotes: 2

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