Generate All Replacements for List of Lists-CodePudding

I'm building an application in Python where I need to define the following sort of function:

generate_replacements(['a', 'b', ['c', ['e', 'f']]], 1)

The expected output is all possible versions of the input list where just one element has been replaced

[
[1, 'b', ['c', ['e', 'f']]],
['a', 1, ['c', ['e', 'f']]],
['a', 'b', 1],
['a', 'b', [1, ['e', 'f']]],
['a', 'b', ['c', 1]],
['a', 'b', ['c', [1, 'f']]],
['a', 'b', ['c', ['e', 1]]]
]

I can see that recursion is the way to go, but I'm really stuck figuring out how to even best start this.

CodePudding user response：

You can generate the replacements from the list, then if you notice you are replacing a list, also pass that list back through the function recursively. This is made a bit simpler if you use a generator:

def generate_replacements(l, rep):
    for i in range(len(l)):
        yield l[0:i]   [rep]   l[i 1: ]
        if isinstance(l[i], list):
            yield from (l[0:i]   [rec]   l[i 1: ] 
                        for rec in generate_replacements(l[i], rep))


list(generate_replacements(['a', 'b', ['c', ['e', 'f']]], 1))

This give:

[[1, 'b', ['c', ['e', 'f']]],
 ['a', 1, ['c', ['e', 'f']]],
 ['a', 'b', 1],
 ['a', 'b', [1, ['e', 'f']]],
 ['a', 'b', ['c', 1]],
 ['a', 'b', ['c', [1, 'f']]],
 ['a', 'b', ['c', ['e', 1]]]]