declarations within python class equivalent to _init_?

Question

I was wondering if the declarations put at the top of the python class are equivalent to statements in __init__? For example

import sys

class bla():
    print 'not init'
    def __init__(self):
        print 'init'
    def whatever(self):
        print 'whatever'

def main():
    b=bla()
    b.whatever()
    return 0

if __name__ == '__main__':
    sys.exit( main() )

The output is:

not init
init
whatever

As a sidenote, right now I also get:

Fatal Python error: PyImport_GetModuleDict: no module dictionary!

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.

Any ideas on why this is? Thank you in advance!

That error indicates something's broken about your Python installation. That's a topic for another question. Be sure to include details - which version, which OS, how you got it, etc. — user395760
– user395760, Commented Apr 28, 2012 at 8:21

Mark Byers · Accepted Answer · 2012-04-28 08:22:01Z

6

No, it's not equivalent. The statement print 'not init' is run while the class bla is being defined, even before you instantiate an object of type bla.

>>> class bla():
...    print 'not init'
...    def __init__(self):
...        print 'init'
not init

>>> b = bla()
init

answered Apr 28, 2012 at 8:22

Mark Byers

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Comments

jgritty · Accepted Answer · 2012-04-28 08:22:17Z

0

They aren't exactly the same, because if you do c=bla() afterwards it will only print init

Also, if you reduce your main() to just return 0 it still prints the not init.

answered Apr 28, 2012 at 8:22

jgritty

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Comments

cobie · Accepted Answer · 2012-04-28 08:23:00Z

0

Declarations such as that are for the whole class. If print was a variable assignment rather a print statement then the variable would be a class variable. This means that rather than each object of the class having its own, there is only one of the variable for the whole class.

answered Apr 28, 2012 at 8:23

cobie

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Comments

CadentOrange · Accepted Answer · 2012-04-28 08:45:25Z

0

They are not equivalent. Your print statement outside the init method is only called once, when he class is defined. For example, if I were to modify your main() routine to be the following:

def main():
    b=bla()
    b.whatever()
    c = bla()
    c.whatever()
    return 0

I get the following output:

not init
init
whatever
init
whatever

The not init print statement executes once, when the class is being defined.

edited Apr 28, 2012 at 8:45

answered Apr 28, 2012 at 8:23

CadentOrange

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2 Comments

jadkik94 Over a year ago

The print statement is executed once, when the class is defined, not when an instance of it is first created. But then you say it correctly in the last sentence...

CadentOrange Over a year ago

Thanks, I've edited it to make is clearer that print would be called when class is defined and it's independent of class instantiation.

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