Converting tuple of lists of variable length into dictionary

[Denis McMahon]

On Sun, 18 Oct 2015 03:17:18 -0700, Beppe wrote:

> hi to everybody, I must turn a tuple of lists into a dictionary.

I went down a different path to Peter, and discovered something 
perplexing:

This failed:

d = { i: deepcopy(l).remove(i) for l in t for i in l }

So I tried to expand it out to see where the issue was, and ended up with 
two variants:

def f1(l, i):
    m = deepcopy(l)
    m.remove(i)
    return m

d = { i: f1(l,i) for l in t for i in l }

def f2(l, i):
    m = deepcopy(l).remove(i)
    return m

d = { i: f2(l,i) for l in t for i in l }

The first variant using, m = deepcopy(l); m.remove(i) works fine, 
generating:

{'a': ['b', 'c', 'd', 'e', 'f'], 'c': ['a', 'b', 'd', 'e', 'f'], 'b': 
['a', 'c', 'd', 'e', 'f'], 'e': ['a', 'b', 'c', 'd', 'f'], 'd': ['a', 
'b', 'c', 'e', 'f'], 'g': ['h', 'i'], 'f': ['a', 'b', 'c', 'd', 'e'], 'i': 
['g', 'h'], 'h': ['g', 'i'], 'm': ['l', 'n', 'o'], 'l': ['m', 'n', 'o'], 
'o': ['l', 'm', 'n'], 'n': ['l', 'm', 'o']}

The second variant using, m = deepcopy(l).remove(i) fails thus:

{'a': None, 'c': None, 'b': None, 'e': None, 'd': None, 'g': None, 'f': 
None, 'i': None, 'h': None, 'm': None, 'l': None, 'o': None, 'n': None}

I'm not sure I understand why after m = deepcopy(l); m.remove(i); m is a 
different value to that which it as after m = deepcopy(l).remove(i).

-- 
Denis McMahon, denismfmcmahon at gmail.com