replace letters in python string

Question

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. :/

split the 'word' string to a list contain individual words and loop through it while check it with endswith — user1655072
– user1655072, Commented Mar 20, 2013 at 15:46
It would be good if you show your input, output and expected output. — dmg
– dmg, Commented Mar 20, 2013 at 15:51
I have no idea about French, but usually grammar is very complex and not always regular (especially not based on two characters within words), so I doubt you’ll be able to get any well working solution using simple search&replaces… — poke
– poke, Commented Mar 20, 2013 at 15:57
actualy thats a very valid point, thing is for past participle there is a very definete way of doing it, its exact — user2191568
– user2191568, Commented Mar 20, 2013 at 16:03

Anuvrat Parashar · Accepted Answer · 2013-03-20 15:54:34Z

2

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.

answered Mar 20, 2013 at 15:54

Anuvrat Parashar

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Comments

ornoone · Accepted Answer · 2013-03-20 16:06:42Z

0

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

answered Mar 20, 2013 at 16:06

ornoone

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Comments

Mahdi-bagvand · Accepted Answer · 2013-03-20 15:57:39Z

0

excuse me

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

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

answered Mar 20, 2013 at 15:57

Mahdi-bagvand

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Comments

yoniLavi · Accepted Answer · 2013-03-20 16:30:27Z

0

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"

answered Mar 20, 2013 at 16:30

yoniLavi

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Comments

James Harvey · Accepted Answer · 2018-03-31 07:37:50Z

0

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"

answered Mar 31, 2018 at 7:37

James Harvey

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