Dictionary and List

[Fredrik Lundh]

sorot at my-deja.com wrote:
> I'm using python 1.5.1. While i'm writing the part of python script
> like this
> 
> ## Part of script ##
> my_list = []
> my_dict = {'a':'','b':[]}
> x = ['a','b','c','d']
> for i in range(0,len(x)):
>    my_dict['a'] = x[i]
>    my_list.append(my_dict)
> 
> print my_list
> ## end ##
> 
> The out put should be like
> my_list = [{'a':'a','b':[]},{'a':'b','b':[]},{'a':'c','b':[]},
> {'a':'d','b':[]}]

nope.  Python is all about references: since you're
using the *same* my_dict in all cases, the list will end
up with four references to my_dict.  not four distinct
dictionaries.

to get distinct copies, move the my_dict assignment
inside the loop, or use the copy module.

</F>

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