CODEWITHSUNDEEP
pythonlisttuples
elnino
elnino

Reputation: 173

How to unpack single-item tuples in a list of lists

I have this form of a list of lists:

[[('1st',), ('2nd',), ('5th',)], [('1st',)]]

I want to convert this to:

[['1st', '2nd', '5th'], ['1st']]

I tried this:

res = [list(ele) for ele in racer_placement for ele in ele]

But the result I got:

[['1st'], ['2nd'], ['5th'], ['1st']]

Upvotes: 0

Views: 1590

Answers (3)

Qudus
Qudus

Reputation: 1520

List = [[('1st',), ('2nd',), ('5th',)], [('1st',)]]
Parentlist = [] 
Temp=[] 
for childlist in List:
     Temp=[] 
     for x in childlist
          Temp.Add(x[0]) 
     parentlist.Add(Temp)

This is untested.

Upvotes: 0

ShadowRanger
ShadowRanger

Reputation: 155684

You need nested comprehensions (with either a two layer loop in the inner comprehension, or use chain.from_iterable for flattening). Example with two layer loop (avoids need for imports), see the linked question for other ways to flatten the inner list of tuples:

>>> listolists = [[('1st',), ('2nd',), ('5th',)], [('1st',)]]
>>> [[x for tup in lst for x in tup] for lst in listolists]
[['1st', '2nd', '5th'], ['1st']]

Note that in this specific case of single element tuples, you can avoid the more complicated flattening with just:

 >>> [[x for x, in lst] for lst in listolists]

per the safest way of getting the only element from a single-element sequence in Python.

Upvotes: 6

tdelaney
tdelaney

Reputation: 77407

You can use slicing to replace the contents of the first level of lists with a new list built from the first element of the tuples.

>>> racer_placement = [[('1st',), ('2nd',), ('5th',)], [('1st',)]]
>>> for elem in racer_placement:
...     elem[:] = [elem2[0] for elem2 in elem]
... 
>>> racer_placement
[['1st', '2nd', '5th'], ['1st']]

Since this is updating the inner list, any other reference to those lists would also see the change. That could be great or disasterous.

Upvotes: 0

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