creating a function for for-loop across specific set of ranges in python

Question

How can you loop across multiple different ranges. for example say i want to run a for loop for specific set of ranges

1 to 2, 4 to 6 and 10 to 13,

I don't know the exact final number so maybe a function might be useful.

The standard method of

for i in range(1,2) + range (4,6) + range (10,13)

I should have this

[1,4,5,6,10,11,13]

My question is, this is not so efficient, if i don't know the total number of ranges am covering, and I can't even create this as a function without so many parameters.

so if i want to have something like this

for i in range(a,b) + range (c,d) + range (e,f), .....

but as a simple function Can someone help with an efficient way of doing this ?

The call range(1,2) returns 1 not 1 and 2

saloua
– saloua

2021-05-15 14:35:49 +00:00
Commented May 15, 2021 at 14:35 — saloua
– saloua, Commented May 15, 2021 at 14:35

atru · Accepted Answer · 2021-05-15 14:48:05Z

4

Simple, though most likely the least efficient solution is to use a nested for loop,

def multi_range_loop(ranges):

    all_values = []
    for rg in ranges:
        for i in range(rg[0], rg[1]):
            all_values.append(i)
    print(all_values)

my_ranges = [[1,3],[4,7],[10,14]]
multi_range_loop(my_ranges)

answered May 15, 2021 at 14:48

atru

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pakpe · Accepted Answer · 2021-05-15 14:47:12Z

2

You can chain the ranges with itertools:

from itertools import chain

total_range = chain(range(1,2), range(4,6), range(10,13))

print(list(total_range))
#[1, 4, 5, 10, 11, 12]

Here is another solution with a function that returns a generator:

def total_range(lst):
    return (i for tup in lst for i in range(tup[0], tup[1]))

list_of_ranges = [(1,2), (4,6), (10,13)]
print(list(total_range(list_of_ranges)))

edited May 15, 2021 at 14:47

answered May 15, 2021 at 13:53

pakpe

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3 Comments

bozzfeedz Over a year ago

this doesn't solve the problem. I need it as a function

pakpe Over a year ago

What are the arguments for your desired function? A list of ranges? If so, you can easily incorporate this code in a function.

pakpe Over a year ago

@mufty__py See my amended answer. I created a function that takes in a list of tuples that correspond to a discontinuous range and returns a generator that can be used like a range.

saloua · Accepted Answer · 2021-05-15 15:17:55Z

1

To have an iterable object from the list of iterable form the different ranges you can use the chain function as in the following response https://stackoverflow.com/a/67547449/1287983.

And in order to have dynamic ranges in a function you can do the following:

def get_ranges(list_ranges):
    lower_bounds, upper_bounds = zip(*list_ranges)
    return list(chain(*list(map(
        range, lower_bounds, upper_bounds))))

get_ranges([(1,2), (4,6), (10,13)])

[1, 4, 5, 10, 11, 12]

The function above returns the list of values. And if you want to iterate efficiently over the resulting values, you just need to return the iterator instead of the list. See the code below.

def get_ranges(list_ranges):
    lower_bounds, upper_bounds = zip(*list_ranges)
    return chain(*list(map(range, lower_bounds, upper_bounds)))

for val in get_ranges([(1,2), (4,6), (10,13), (2,5)]):
    print(val)

1 4 5 10 11 12 2 3 4

edited May 15, 2021 at 15:17

answered May 15, 2021 at 14:36

saloua

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2 Comments

bozzfeedz Over a year ago

How can this be used in a for loop?

saloua Over a year ago

@mufty__py I edited the response by adding the way to use the result in a for loop.

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