calling function in a loop for several lists python

Question

I have written a function in python which takes three input variables. Now I want to call the function on a list of items for each input variables. So the function call is like this:

 call_function('cat', 'brown', 2)

The lists are:

 category_list = ['cat', 'dog', 'squirrel']
 color_list = ['brown', 'black']
 age = [1,2,3]

Now I want to run function on each item. So it should return results for cat, brown and 1, and then cat, brown and 2, and then cat, brown and 3 and then cat, black and 1, and then cat, black and 2, and then cat, black and 3 and then do the same for dog and then for squirrel. I know that I will need to call the function in a loop, but I tried and failed several times. Could someone please help me with this?

X3R0 · Accepted Answer · 2022-06-24 14:50:06Z

1

use itertools, it does the job for you, really simple to call the product function.

supply the variables to itertools.product(....)) as paramaters then list() the response.

Code

import itertools
category_list = ['cat', 'dog', 'squirrel']
color_list = ['brown', 'black']
age = [1,2,3]

def call_function(category, color, age):
    print(category, color, age)


combinations = list(itertools.product(category_list, color_list, age))
for combintaion in combinations:
    call_function(combintaion[0], combintaion[1], combintaion[2])

Output

cat brown 1
cat brown 2
cat brown 3
cat black 1
cat black 2
cat black 3
dog brown 1
dog brown 2
dog brown 3
dog black 1
dog black 2
dog black 3
squirrel brown 1
squirrel brown 2
squirrel brown 3
squirrel black 1
squirrel black 2
squirrel black 3

Proof

Test Here

code for method from itertools

def product(*args, repeat=1):
    # product('ABCD', 'xy') --> Ax Ay Bx By Cx Cy Dx Dy
    # product(range(2), repeat=3) --> 000 001 010 011 100 101 110 111
    pools = [tuple(pool) for pool in args] * repeat
    result = [[]]
    for pool in pools:
        result = [x+[y] for x in result for y in pool]
    for prod in result:
        yield tuple(prod)

edited Jun 24, 2022 at 14:50

answered Jun 24, 2022 at 13:40

X3R0

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18 Comments

user18334254 Over a year ago

where exactly am I calling the function here?

user18334254 Over a year ago

gives me this error: TypeError: string indices must be integers. Think it is expecting a string for age

user18334254 Over a year ago

yes, I gave commas. So maybe missing single quotes for non-numerical list items?

user18334254 Over a year ago

please look at my question, how I call the function for it to work. I edited to make it clearer

acushner Over a year ago

no reason to call list on the result of product. it just creates a list when all you need is one element at a time.

|

Naveed · Accepted Answer · 2022-06-24 15:57:10Z

1

here is another way to do it, using pd.apply, after creating a dataframe using itertools.product

import itertools  

category_list = ['cat', 'dog', 'squirrel']
color_list = ['brown', 'black']
age = [1,2,3]

df=pd.DataFrame.from_records(
    list(itertools.product(
        category_list, color_list, age
    )), columns=['category', 'color', 'age'])

df.apply(lambda row: call_function(row['category'], row['color'], row['age']), axis=1)

RESULT:

cat brown 1
cat brown 2
cat brown 3
cat black 1
cat black 2
cat black 3
dog brown 1
dog brown 2
dog brown 3
dog black 1
dog black 2
dog black 3
squirrel brown 1
squirrel brown 2
squirrel brown 3
squirrel black 1
squirrel black 2
squirrel black 3

if function is named MY_FUNCTION

df.apply(lambda row: MY_FUNCTION(row['category'], row['color'], row['age']), axis=1)

edited Jun 24, 2022 at 15:57

answered Jun 24, 2022 at 14:28

Naveed

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12 Comments

user18334254 Over a year ago

I get this error: df=pd.DataFrame.from_records( ^ SyntaxError: cannot assign to function call

Naveed Over a year ago

updated solution with the import line

user18334254 Over a year ago

yes, first thing I did

Naveed Over a year ago

added screenshot of my notebook

user18334254 Over a year ago

ok, I see the output, but I need each output to be called on my_function. my_function(cat, brown, 1), etc How can I put each output as input into my_function and get the report on each combination?

|

user18334254 · Accepted Answer · 2022-06-25 07:13:52Z

0

I solved it by calling the function in a loop. I am sure there is a more efficient/elegant way to do this, but since my df and lists are small, it works good. Wanted to post my solution for those who are working with small lists and having similar problem. Of course, improvement suggestions are welcome.

for i in category_list: 
    for j in color_list: 
        for k in age: 
            call_function(i,j,k)

edited Jun 25, 2022 at 7:13

answered Jun 25, 2022 at 7:01

user18334254

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