How to create a function for recursively generating iterating functions

Question

I currently have a bit of Python code that looks like this:

for set_k in data:
    for tup_j in set_k:
        for tup_l in tup_j:

The problem is, I'd like the number of nested for statements to differ based on user input. If I wanted to create a function which generated n number of for statements like those above, how might I go about doing that?

You could seperate the loop into a function, then you could recursively call the function. Exactly how it would work though would depend on the use case. — Carcigenicate
– Carcigenicate, Commented Mar 1, 2018 at 22:28

wim · Accepted Answer · 2018-03-01 22:35:42Z

8

def nfor(data, n=1):
    if n == 1:
        yield from iter(data)
    else:
        for element in data:
            yield from nfor(element, n=n-1)

Demo:

>>> for i in nfor(['ab', 'c'], n=1):
...     print(i)
...     
ab
c
>>> for i in nfor(['ab', 'c'], n=2):
...     print(i)
...     
a
b
c

edited Mar 1, 2018 at 22:35

answered Mar 1, 2018 at 22:32

wim

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6 Comments

Brendan Abel Over a year ago

Note that the yield from syntax is Python 3 only.

wim Over a year ago

Is it really worth noting a 5+ years old feature of the language any more?

Chris Over a year ago

Python 3.3 to be exact @BrendanAbel.

Chris Over a year ago

Eh, I think many people still use Python 2 for legacy code @wim. OTHO, I think you do have a point. If people still haven't ported to Python 3 by now, that's not really your problem.

Chris Over a year ago

Yeah, I know Python's ending support for Python 2 in 2020. Like I said, there are still people out their who for one reason or another haven't ported their legacy code to Python 3. In my opinion, and Given SO's popularity, I would note that code in my uses certain Python 3 features. But I do understand where you're coming from.

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