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a = b = ['a', 'b'] 
b = ['x', 'y'] # reassigns the name b
print a # still the original list

a = b = ['a', 'b']
b[:] = ['x', 'y'] # changes the existing list bound to a 
print a # a changed too

How come a is linked to b? What kind of mechanism does python use to handle chained assignments of mutable data types?

Maaverik
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  • *"What kind of mechanism does python use to handle chained assignments of mutable data types?"* - no particular mechanism, it just assigns the same object to multiple names; it's the same as doing `a = [...]` then `b = a`. – jonrsharpe Mar 17 '16 at 09:40
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    *How come a is linked to b?* possibly because you said `a = b` – Tim Mar 17 '16 at 09:40

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