Hi there,
I've just managed to nail down a bug which took me nearly two whole
days to find: this is coming from an unexpected (at least from me)
behaviour of numpy.
I understand that if foo is a numpy array, doing bar = foo makes no
copy, and whenever you change the value of foo, you change the value of bar:
import numpy as N
foo = N.linspace(0, 4, 5)
bar = foo
print foo[1]
bar[1] = -1
print foo[1]
=> prints 1 and -1.
Now, if I do:
bar += 1
print bar is foo
prints True
But if I do bar = bar + 1, then bar is not a copy of foo anymore. Is
this intended ? This looks really confusing to me, and I would like to
know what the precise rules about copy vs alias are ?
Cheers,
David
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