CODEWITHSUNDEEP
pythonlistzipiterabletry-except
alvas
alvas

Reputation: 122142

Checkan iterable after expanding the iterations using zip?

How to check whether an iterable is the same size after expanding the iterations using zip? E.g.

>>> x = iter([1,2,3])
>>> y = iter([5,6,7,8])
>>> for i,j in zip(x,y):
...     print i,j
... 
1 5
2 6
3 7

Doing next(x) after using up the iterable throws an error but i can't try-except it since it's not an Error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration

Is there any way to do the check in a single pass?

Upvotes: 2

Views: 63

Answers (3)

zvone
zvone

Reputation: 19362

Depending on what you are trying to achieve, if you are interested in all values from the itreables, you might consider using itertools.izip_longest rather than zip:

>>> import itertools
>>> x = iter([1,2,3])
>>> y = iter([5,6,7,8])
>>> for i, j in itertools.izip_longest(x, y, fillvalue=None):
...     print i, j
...
1 5
2 6
3 7
None 8

Upvotes: 1

Padraic Cunningham
Padraic Cunningham

Reputation: 180461

next also takes a default value so you can simply use that:

if next(x, None):
   # x is not empty

Just make sure to use a default that won't be appearing in your iterable.

It is also possible to use __length_hint__:

In [4]: x = iter([1, 2, 3])

In [5]: y = iter([5, 6, 7, 8])

In [6]: for i, j in zip(x, y):
   ...:         print(i, j)
   ...:     
(1, 5)
(2, 6)
(3, 7)

In [7]: x.__length_hint__()
Out[7]: 0

In [8]: y.__length_hint__()
Out[8]: 1

Upvotes: 3

Liari
Liari

Reputation: 116

What do you mean you can't try-except?

try:
    x.next()
except StopIteration:
    pass

Upvotes: 3

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