Dynamic For Loops In Python

i understand that to create dynamic for loops, recursive or itertools module in python is the way to go. Lets say I am doing it in recursive. What I want is for var1 in range(var1_

Solution 1:

Use the itertools.product() function to generate the values over a variable number of ranges:

forvaluesin product(*(range(*b) for b in boundaries_list)):
    # do things with the values tuple, do_whatever(*values) perhaps

Don't try to set a variable number of variables; just iterate over the values tuple or use indexing as needed.

Using * in a call tells Python to take all elements of an iterable and apply them as separate arguments. So each b in your boundaries_list is applied to range() as separate arguments, as if you called range(b[0], b[1], b[2]).

The same applies to the product() call; each range() object the generator expression produces is passed to product() as a separate argument. This way you can pass a dynamic number of range() objects to that call.

Solution 2:

Just for fun, I thought that I would implement this using recursion to perhaps demonstrate the pythonic style. Of course, the most pythonic way would be to use the itertools package as demonstrated by Martijn Pieters.

defdynamic_for_loop(boundaries, *vargs):
    ifnot boundaries:
        print(*vargs) # or whatever you want to do with the valueselse:
        bounds = boundaries[0]
        for i inrange(*bounds):
            dynamic_for_loop(boundaries[1:], *(vargs + (i,)))

Now we can use it like so:

In [2]: boundaries = [[0,5,1], [0,3,1], [0,3,1]]

In [3]: dynamic_for_loop(boundaries)
000001002010011012020021022100101102110111112120121122200201202210211212220221222300301302310311312320321322400401402410411412420421422