CODEWITHSUNDEEP
pythonstring
alicew
alicew

Reputation: 275

concatenating strings?

def change(s):
    s = s + "!"


word = "holiday"
change(word)    
print word

how come the output of this is "holiday" instead of "holiday!"? Is it because the 3 line of codes are outside the function? If so, why would it matter if it's outside the function since it's after the change function?

Upvotes: 6

Views: 300

Answers (5)

Óscar López
Óscar López

Reputation: 236150

Try this:

def change(s):
    return s + "!"

Use it like this:

word = 'holiday'
print change(word)

Or like this:

word = 'holiday'
word = change(word)
print word

Be aware that any modifications you do to a parameter string inside a function will not be seen outside the function, as the s parameter in the function is local to the scope of the function, and any changes you do (like in the code in the question) will only be visible inside the function, not outside. All function parameters in Python are passed by value.

Upvotes: 6

jamylak
jamylak

Reputation: 133764

s in change(s) is a name that is bound to the value of word when you call change(word).

In the line s = s + "!" you are binding s to a new string which is created by concatenating the value bound to s and !, not doing anything to word.

Also it is best not to have side effects even if it is possible so returning a new value is better.

def change(s):
    return s + '!'

Upvotes: 1

jbreicis
jbreicis

Reputation: 588

You are passing a 'copy' of word rather that word instance to the function. Therefore changes are applied to the copy of word you hold in s variable inside the function

Upvotes: 1

Simeon Visser
Simeon Visser

Reputation: 122536

You are only modifying the local variable s in the function change. This does not modify the variable word. If you wish to modify word, you need to return the result of change and assign it to word:

def change(s):
    s = s + "!"
    return s


word = "holiday"
word = change(word)    
print word

Upvotes: 3

Niall Byrne
Niall Byrne

Reputation: 2460

You aren't returning the value from change.

Try:

def change(s):
    s = s + "!"
    return s


word = "holiday"
word = change(word)    
print word

So in the above example, s is being modified, and then word is reassigned the modified value.

Upvotes: 1

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