regex help?

ok i'm not sure if i can use regex to do this it'd be great if you can give some suggestions!

i have a list of pure numbers in one hand
and another list of also numbers but with dashes.

it's like this:
list1 = [245366556346,4534525326562,56345254234237...
list2 = [75465-54224-4,3-55-342526,....

as you can see the postion of dash changes.
given that all my numbers have same length, how do I introduce dash to exactly the same way to pure number list?

what i mean is if I have 12345 in list 1 and 76-543 in list 2, i want to create a list that has 12-345.

[Gribouillis]

Here is a possible solution without regexes

def add_dash(str1, str2):
    src = iter(str2)
    return "".join('-' if x == '-' else next(src) for x in str1)

s1 = "75465-54224-4"
s2 = "245366556346"

print add_dash(s1, s2)

"""my output -->
24536-65563-4
"""

Notice that the 6 at the end of s2 was lost because s1 has 11 digits and s2 has 12 digits, which contradicts your statement that all numbers have the same length.

[TrustyTony]

Here alternative without iterator, which leaves extra digits:

def add_dash(control, to_add):
    as_list = list(to_add)
    p = 0
    while '-' in control[p:]:
        p = control.find('-', p) + 1
        as_list.insert(p - 1, '-')
    return ''.join(as_list)


s1 = "75465-54224-4"
s2 = "245366556346"

print add_dash(s1, s2)

"""my output -->
24536-65563-46
"""

[Gribouillis]

You can leave extra digits with generators too

from itertools import chain

def add_dash(str1, str2):
    src = iter(str2)
    return "".join(chain(('-' if x == '-' else next(src) for x in str1), src))