CODEWITHSUNDEEP
pythonlist-comprehension
The Condor
The Condor

Reputation: 1054

Extract values from list and make tuples

I need a simple thing but I cannot do it:

list = 'SBEDFG'

I need as output:

[(S,B),(B,E),(E,D),(D,F),(F,G)]

This is what I tried:

[(list[ind],list[ind+1]) for ind,i in list]

But it gives me this error:

ValueError: need more than 1 value to unpack

Can you help me? Thanks!

Upvotes: 2

Views: 73

Answers (3)

user3273866
user3273866

Reputation: 604

>>>b=[]
>>> for ind,i in enumerate(list):
...  if ind < len(list)-1:
...   b.append((list[ind],list[ind+1]))
...
>>> print b
[('S', 'B'), ('B', 'E'), ('E', 'D'), ('D', 'F'), ('F', 'G')]

Upvotes: 0

Paulo Bu
Paulo Bu

Reputation: 29794

You can simply use zip() function like this:

>>>l = 'SBEDFG'
>>>zip(l,l[1:])
[('S', 'B'), ('B', 'E'), ('E', 'D'), ('D', 'F'), ('F', 'G')]

With Python 3.X you'll need to convert the zip result to a list:

#Python 3.X
>>>l = 'SBEDFG'
>>>list(zip(l,l[1:]))
[('S', 'B'), ('B', 'E'), ('E', 'D'), ('D', 'F'), ('F', 'G')]

With list comprehension I would do it with range() function:

>>>[(l[i],l[i+1]) for i in range(len(l)-1)]
[('S', 'B'), ('B', 'E'), ('E', 'D'), ('D', 'F'), ('F', 'G')]

Hope this helps!

Upvotes: 5

Neel
Neel

Reputation: 21243

try this

>>> [(list[i-1], list[i]) for i in range(1, len(list))]
[('S', 'B'), ('B', 'E'), ('E', 'D'), ('D', 'F'), ('F', 'G')]

Upvotes: 2

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