Python: Print a list with recursion

Question

I have these two test cases:

calc1 = [['print', 5]] # 5
calc2 = [['print', 2], ['print', 4], ['print', 8]] # 2 4 8

And I can print them correctly with this function:

def exec_program(p):
    if len(p) == 1:
        print(p[0][1])
    else:
        for i in p:
            print(i[1])

print(exec_program(calc2))
>>> 2
>>> 4
>>> 8

But how can I solve this recursively? The number of items in calc can be 1 or many. All help appreciated

Edit: My current try. Looking for a solution

def exec_program(p):
    if len(p) == 1:
        print(p[0][1])
    else:
        print(exec_program[1:] - 1)

Have you tried your recursive version? Does it produce the right output? Are there any errors? — quamrana
– quamrana, Commented Nov 6, 2022 at 19:40

Chris · Accepted Answer · 2022-11-06 19:43:33Z

2

def do_print(calc):
    if not calc:
       return
    if calc[0] == 'print':
        print(calc[1])
    else:
        for subcalc in calc:
            do_print(subcalc)

That will work for any depth of nested lists.

You will want to add some error checking on the inputs, better yet use some more strict data structure such as a NamedTuple.

answered Nov 6, 2022 at 19:43

Chris

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1 Comment

Ghazi Over a year ago

Nice solution, you took the first element of every list in account, assuming that it might change from print to a different functionality.

Ghazi · Accepted Answer · 2022-11-06 19:41:54Z

0

you can slice the list starting from the next element whenever you are done with printing an element, an example:

calc2 = [['print', 2], ['print', 4], ['print', 8]]
def print_me(calc2):
    if not calc2:
       return     #once calc2 is empty, we stop the recursion.
     print(calc2[0][1])
     return print_me(calc2[1::])
print_me(calc2)

edited Nov 6, 2022 at 19:41

answered Nov 6, 2022 at 19:36

Ghazi

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2 Comments

tobias_k Over a year ago

Agreed, I meant this to soften my critique, not to add more critique. However, on closer inspection OP might mean a different kind of recursion (on depth of nested lists, not on list length).

Ghazi Over a year ago

I will agree with you on this, however it is not clarified why is the op having a nested list for printing elements, so we don't know the goal behind this

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