oop - Accessing variable and functions in object oriented python - python -

1. how declare default value in python object?

without python object looks fine:

def obj(x={123:'a',456:'b'}):     return x fb = obj() print fb 

with python object following error:

def foobar():     def __init__(self,x={123:'a',456:'b'}):         self.x = x     def getstuff(self,field):         return x[field] fb = foobar() print fb.x  traceback (most recent call last):   file "testclass.py", line 9, in <module>     print fb.x attributeerror: 'nonetype' object has no attribute 'x' 

1. how object return value of variable in object?

with python object, got error:

def foobar():     def __init__(self,x={123:'a',456:'b'}):         self.x = x     def getstuff(self,field):         return x[field]  fb2 = foobar({678:'c'}) print fb2.getstuff(678)  traceback (most recent call last):   file "testclass.py", line 8, in <module>     fb2 = foobar({678:'c'}) typeerror: foobar() takes no arguments (1 given) 

you didn't define class, defined function nested functions.

def foobar():     def __init__(self,x={123:'a',456:'b'}):         self.x = x     def getstuff(self,field):         return x[field] 

use class define class instead:

class foobar:     def __init__(self,x={123:'a',456:'b'}):         self.x = x     def getstuff(self, field):         return self.x[field] 

note need refer self.x in getstuff().

demo:

>>> class foobar: ...     def __init__(self,x={123:'a',456:'b'}): ...         self.x = x ...     def getstuff(self, field): ...         return self.x[field] ...  >>> fb = foobar() >>> print fb.x {456: 'b', 123: 'a'} 

do note using mutable value function keyword argument default not idea. function arguments defined once, , can lead unexpected errors, classes share same dictionary.

see "least astonishment" , mutable default argument.