xixiliguo wrote:
c = [1, 2, 3, 4, 5]
class TEST():
c = [5, 2, 3, 4, 5]
def add( self ):
c[0] = 15
a = TEST()
a.add()
print( c, a.c, TEST.c )
result :
[15, 2, 3, 4, 5] [5, 2, 3, 4, 5] [5, 2, 3, 4, 5]
why a.add() do not update c in Class TEST? but update c in main file
Attributes can only accessed by explictly naming the owner, unlike some
other languages which infer 'this/self'.
When an attribute is not found in the owner, python may look into the
"outer" namespace. Read the python documentation for an accurate
description.
Here is an illustration (python 2.5):
c='global'
class TEST():
c = 'class'
d = 'classonly'
def __init__(self):
self.c='instance'
def test(self):
print c
print TEST.c
print self.c
print self.d # this is valid, if d is not found in the instance,
python will look into the class
t = TEST()
t.test()
global
class
instance
classonly
Note that objects in python are properly named namespaces. locals and
globals are not, so be careful while naming those (in few words: don't
use globals)
c = 'global'
def foo():
c = 'local'
print c # same name for 2 different objects
def bar():
print c
global c # the global statement is quite strange, it applies to the
whole block, even previous statements, ppl usually put it at the
begining of the block though
foo()
bar()
'local'
'global'
Cheers,
JM
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