Recursive lambda in Python

Question

I have a structure like this:

{"query": {"or": ["ids": [1,2,3], "text": "some text"]}}

The structure may vary, but the idea is to exclude the value corresponding to "ids" key.

I wrote a spike, but for some reason it doesn't work as expected, maybe a bug in Python? Or what's more probable it's my mistake:

fix = lambda q: {True: {k: '...' if k == 'ids' else fix(v) for k, v in q.items()}, False: {True: [fix(i) for i in q], False: q}[isinstance(q, list)]}[isinstance(q, dict)]

Here is a multiline analogy. It works as expected:

def fix(q):
   if isinstance(q, dict):
       return {k: ('...' if k == 'ids' else fix(v)) for k, v in q.items()}
   else:
       if isinstance(q, list):
           return [fix(i) for i in q]
       else:
           return q

Ming-Tang · Accepted Answer · 2015-11-19 00:16:27Z

1

Hint: You need {True: lambda: A, False: lambda: B}[condition]() to selectively evaluate expressions, or else both branches are evaluated anyways and it might cause errors.

answered Nov 19, 2015 at 0:16

Ming-Tang

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Comments

Dan D. · Accepted Answer · 2015-11-19 00:22:12Z

0

You can just use more A if C else B

fix = lambda q: ({ k: '...' if k == 'ids' else fix(v) for k, v in q.items() }
                 if isinstance(q, dict) else
                 ([fix(i) for i in q] if isinstance(q, list) else q))

answered Nov 19, 2015 at 0:22

Dan D.

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