Enumerate object is destroyed by casting?

[Nick Jacobson]

Casting an 'enumerate' object destroys it?? Is that supposed to
happen, or is it a bug?


For example:
a = ['a', 'b', 'c']
e = enumerate(a)
print dict(e)
print dict(e)


Result:
{0: 'a', 1: 'b', 2: 'c'}
{}

 

[Jeffrey Froman]

Casting an 'enumerate' object destroys it??  Is that supposed to
happen, or is it a bug?


For example:
a = ['a', 'b', 'c']
e = enumerate(a)
print dict(e)
print dict(e)


Result:
{0: 'a', 1: 'b', 2: 'c'}
{}

This is supposed to happen. Enumerate objects are essentially generators --
casting the object doesn't "destroy" it; but iterating over its values
"uses them up". In other words, after the first dict() call, your
enumerator is now empty. The same thing would happen if you simply iterated
over the object, like:

for thing in e:
print thing

 

[Shalabh Chaturvedi]

Casting an 'enumerate' object destroys it?? Is that supposed to
happen, or is it a bug?


For example:
a = ['a', 'b', 'c']
e = enumerate(a)
print dict(e)
print dict(e)


Result:
{0: 'a', 1: 'b', 2: 'c'}
{}

This is not casting (there is no casting in Python). It is creating a
new dict from an iterable. enumerate(a) creates an iterable that runs
over the items *once*. After that there is nothing left to return.

HTH,

Shalabh