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I have defined a generator that yields log entries from Elasticsearch:
def gen():
....
for hit in results:
yield hit
How can I loop through two elements at the same time? Something in the lines of:
for one, two in gen():
...
By two elements I mean this: A, B, B, C, ..., Y, Z (for a generated list of A, B, ..., Y, Z).
809
Simply speaking, a generator is a function that returns an object (iterator) which we can iterate over (one value at a time).
You need to call next() or loop through the generator object to access the values produced by the generator expression. When there isn't the next value in the generator object, a StopIteration exception is thrown. A for loop can be used to iterate the generator object.
In the above example, the mygenerator() function is a generator function. It uses yield instead of return keyword. So, this will return the value against the yield keyword each time it is called. However, you need to create an iterator for this function, as shown below.
A Python generator is a function that produces a sequence of results. It works by maintaining its local state, so that the function can resume again exactly where it left off when called subsequent times. Thus, you can think of a generator as something like a powerful iterator.
This answer assumes you want non-overlapping pairs. You can do this via zip() because the iterator is consumed:
for one, two in zip(gen, gen):
# do something
Example:
>>> gen = (x for x in range(5))
>>> for one, two in zip(gen, gen): print(one,two)
...
0 1
2 3
Note, as timgeb commented, you should use itertools.zip_longest if you have an uneven number of elements and you want the last one with a fill value, for example:
>>> gen = (x for x in range(5))
>>> for one, two in zip_longest(gen, gen): print(one, two)
...
0 1
2 3
4 None
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