CODEWITHSUNDEEP
pythonreplace
futureExpert
futureExpert

Reputation: 156

Variable re-use in replace()

I have a simple replace() using a dict. This code is fully functional, but as soon as I change to a new variable name for the cleaned string, it stops working (step 2). My question is why I cannot create a new string (s2) in the second step?

words = {
    "badword": "niceword",
    "worseword": "nicerword"
    }
#step1
sentence = input(">")
for key, value in words.items():
    sentence = sentence.replace(key, value)
print(sentence)
#step2
sentence2 = input("s2>")
for key, value in words.items():
    s2 = sentence2.replace(key, value) #here
print(s2)

Upvotes: 0

Views: 34

Answers (2)

Vanillaboy
Vanillaboy

Reputation: 412

There is a problem with your logic.

You are doing it in two different ways

sentence = input(">")
for key, value in words.items():
    sentence = sentence.replace(key, value)

You replace something in sentence for each item in your dict

As in this block you are doing it the wrong way

sentence2 = input("s2>")
for key, value in words.items():
    s2 = sentence2.replace(key, value) #here
print(s2)

sentence2 is not the string that will be modified, you just save in s2 the result of sentence2.replace() So you overwrite s2 each time with the original inputstring.

Upvotes: 1

MatsLindh
MatsLindh

Reputation: 52792

To keep the original string as well you'll have to copy the string before doing replacements, and then do the replacements on the copy.

s2 = sentence2 = input("s2>")

for key, value in words.items():
    s2 = s2.replace(key, value) #here

print(sentence2, s2)

Otherwise you're overwriting s2 in each iteration, using the unaltered sentence2 as your source - in effect only having the last iteration of the loop matter (which replaces worseword with nicerword.

With your original code each step of the loop looks like this, with "badword worseword" as input:

s2 = "badword worseword".replace('badword', 'niceword')

# s2 is now niceword worseword
# but since you're still using sentence2, which is "badword worseword", the second
# iteration will still use the original string and not the changed one:
s2 = "badword worseword".replace('worseword', 'niceword')

.. and now s2 is badword niceword - since you're not using s2 but sentence2 as the string you're replacing content in in your loop.

Upvotes: 1

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