CODEWITHSUNDEEP
pythonsyntax
THeBAckwardss
THeBAckwardss

Reputation: 27

% vs. + as related to strings in Python?

This:

hilarious = False
joke_evaluation = "Isn't that joke so funny?! %r"

print joke_evaluation % hilarious

and this:

w = "This is the left side of..." e = "a string with a right side."

print w + e

Seem to be doing the same thing. Why can't I change the code to read:

print joke_evaluation + hilarious

Why doesn't this work?

Upvotes: 1

Views: 194

Answers (4)

starlord
starlord

Reputation: 1

This was quite confusing to me as well, but it seems that due to it being a Boolean value you cannot use +.

If you do you get an error like this:

TypeError: cannot concatenate 'str' and 'bool' objects

Upvotes: 0

THeBAckwardss
THeBAckwardss

Reputation: 27

This is what was confusing me:

hilarious = False
joke_evaluation = "Isn't that joke so funny?! %r"

print joke_evaluation % hilarious

I would prefer it to look like this:

hilarious = False
joke_evaluation = "Isn't that joke so funny?! %r" % hilarious

print joke_evaluation

I guess it just looked funky to my eyes.

Upvotes: 0

Alex L
Alex L

Reputation: 8925

%r calls repr(), which represents False (bool) as "False" (string).

+ can only be used to concatenate a string with other strings (Otherwise you get a TypeError: cannot concatenate 'str' and 'bool' objects)

You can convert False to a string before you concatenate it:

>>> print "Isn't that joke so funny?!" + str(False)

You could also try new string formatting:

>>> print "Isn't that joke so funny?! {!r}".format(False)
Isn't that joke so funny?! False

Upvotes: 6

wibarr
wibarr

Reputation: 276

This is a type conversion issue. When you are trying to concatenate to a string in Python, you may only concatenate other strings. You are attempting to concatenate a Boolean value to a string, which is not a supported operation.

You could do 

print w + str(e)

and that would be functional.

Upvotes: 3

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