CODEWITHSUNDEEP
pythonloopsfor-loopwhile-loopiterator
Intrastellar Explorer
Intrastellar Explorer

Reputation: 2451

Python how to make loop that can be "for" or "while", depending on if upper limit is present

I have a use case where I need to repeat some block of code:

I am wondering, is there some Python built-in way to:

Note: I know I can use an if statement (depending on if upper limit is present), and switch between a for or while loop. I am trying to not have the code block repeated twice, or it broken out into another function.

Current Implementation

I wrote the below flawed (see below) for_while_hybrid.py using Python 3.8.2.

from typing import Iterator


def iter_for_while(num_yield: int = None) -> Iterator[int]:
    """Generate an incrementing counter.

     This enables one to make a for loop or a while loop, depending on args.

    Args:
        num_yield: Number of times to yield.
            If left as None, the generator makes a while loop
            If an integer, the generator makes a for loop

    """
    counter = 0
    condition = True if num_yield is None else counter < num_yield
    while condition:
        yield counter
        counter += 1
        if num_yield is not None:
            condition = counter < num_yield


upper_limit = 5
for _ in iter_for_while(upper_limit):
    print("Some code block")  # Run 5 times

for _ in iter_for_while():
    print("Some code block")  # Run infinitely

This implementation works.

The downside is, if run for a very long time, I am worried the counter will take up lots of memory, or will eventually max out. My computer is 64-bit, so sys.maxsize = 2 ** 63 - 1 = 9,223,372,036,854,775,807.

Upvotes: 0

Views: 188

Answers (2)

chepner
chepner

Reputation: 531718

Just use count or range, depending on the upper bound:

from itertools import count


def iter_for_while(bound=None):
    return count() if bound is None else range(bound)

Upvotes: 6

Evorage
Evorage

Reputation: 503

use a while loop but you can say while X < Y: do something and then X += 1 this means you can control how many times it repeats with X or if you want it indefinitely then don't say X + 1

Upvotes: 1

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