Question

Possible Duplicate:
Flatten (an irregular) list of lists in Python

for instance, from:

[[1,2,3],'a',[[4],[5,6],7]]

we want to flatten/penetrate the structure and get all the elements at bottom listed in a line:

[1,2,3,'a',4,5,6,7]

Answer 1

# a recursive function to flatten arbitrary nested lists into one simple 1D list
def flatten(inlist,outlist):   
    for e in inlist:
        if isinstance(e,list) :
            flatten(e,outlist)
        else:
            outlist.append(e)

it’s a practice of recursive function, :). the “outlist” here serves as a reference for return-list.

there must be better structures…

😉
for example: