str method in Python

Question

I can't manage to get this __str__ to work. I created a class,

class Hangman :

and then

def __str__(self) : 
return "WORD: " + self.theWord + "; you have " + \
self.numberOfLives + "lives left"

there's an init statement and assignment in the program but I can't get the thing to work! the only way I can do it is by doing this, but surely what's the point of using __str__

def __str__(self) :
    print("WORD: {0}; you have {1} lives left".\
    format(self.theWord,self.numberOfLives))

Code:

theWord = input('Enter a word ')
numberOfLives = input('Enter a number ')
hangman = Hangman(theWord,numberOfLives)
Hangman.__str__(hangman)

Output:

>>> 
Enter a word Word
Enter a number 16
>>>

using the print method, output:

>>> 
Enter a word word
Enter a number 16
WORD: word; you have 16 lives left
>>>

Read this post -> mail.python.org/pipermail/tutor/2004-September/031726.html — Alberto Megía
– Alberto Megía, Commented Nov 27, 2013 at 20:53

poke · Accepted Answer · 2013-11-27 21:03:44Z

5

Hangman.__str__(hangman)

This line will just call the __str__ method. So does this btw. which is the preferred way to do it (in general, don’t call special methods directly):

str(hangman)

str and the __str__ method are just there to convert the object into a string, but not to print it. For example you could just as well log it to a file, so printing wouldn’t always be appropriate.

Instead, if you want to print it, just print it:

print(hangman)

print will automatically call str() on the object and as such use the type’s __str__ method to convert it to a string.

answered Nov 27, 2013 at 21:03

poke

392k80 gold badges596 silver badges632 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

DonnellyOverflow Over a year ago

Ahhhh! Can't believe it's that easy. Thanks a lot!

Ben · Accepted Answer · 2013-11-27 21:06:53Z

0

Hangman.__str__(hangman) isn't a command to print the string representation of hangman, it's an expression that evaluates to the string representation of hangman.

If you type that manually at the interactive prompt, you'll get the value of the expression printed, because the interactive prompt does that as a convenience. Having that line in a script (or in a function you call) will not print anything - you need to actually tell python to print it, with print(hangman).

answered Nov 27, 2013 at 21:06

Ben

72.1k21 gold badges133 silver badges184 bronze badges

Comments

chepner · Accepted Answer · 2013-11-27 21:08:23Z

0

Like this post says: https://mail.python.org/pipermail/tutor/2004-September/031726.html

 >>> class A:
...   pass
...
 >>> a=A()
 >>> print a
<__main__.A instance at 0x007CF9E0>

If the class defines a __str__ method, Python will call it when you call 
str() or print:
 >>> class B:
...   def __str__(self):
...     return "I'm a B!"
...
 >>> b=B()
 >>> print b
I'm a B!

Quoting

To recap: when you tell Python to "print b", Python calls str(b) to get the string representation of b. If the class of b has a __str__ method, str(b) becomes a call to b.__str__(). This returns the string to print.

edited Nov 27, 2013 at 21:08

chepner

538k77 gold badges594 silver badges746 bronze badges

answered Nov 27, 2013 at 21:04

Alberto Megía

2,2553 gold badges23 silver badges33 bronze badges

Comments

BioGeek · Accepted Answer · 2013-11-27 21:09:58Z

0

This code works:

class Hangman(object):

    def __init__(self, theWord, numberOfLives):
        self.theWord = theWord
        self.numberOfLives = numberOfLives

    def __str__(self) :
        return "WORD: " + self.theWord + "; you have " + \
               self.numberOfLives + " lives left"

if __name__ == '__main__':
    theWord = input('Enter a word ')
    numberOfLives = input('Enter a number ')
    hangman = Hangman(theWord,numberOfLives)
    print(hangman)

Output:

>>> 
Enter a word word
Enter a number 16
WORD: word; you have 16 lives left

answered Nov 27, 2013 at 21:09

BioGeek

23k23 gold badges90 silver badges156 bronze badges

Collectives™ on Stack Overflow

str method in Python

4 Answers 4

1 Comment

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related