List of tuples from original list

Question

I have a list [6, 63, 131, 182, 507, 659, 669]

and would like to create a new list of pairs that looks like this:

[(7,63),(64,131),(132,182),(183,507),(508,659),(660,669)]

When I use the below code:

list = [6, 63, 131, 182, 507, 659, 669]
line_num = 0
for idx,i in enumerate(list):
    print(list[idx]+1,list[idx+1])

I get below error:

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
      5     pass
      6 else:
----> 7     print(city_index[idx]+1,city_index[idx+1])

IndexError: list index out of range

How do I end the loop before I get an error?

Asked By: Lee Whieldon

||

Source

Answer 1

l = [6, 63, 131, 182, 507, 659, 669]
new_l = []
for i in range(1, len(l)):
    new_l.append((l[i-1] + 1, l[i]))
print(new_l)

output:

[(7, 63), (64, 131), (132, 182), (183, 507), (508, 659), (660, 669)]

Answered By: 555Russich

Answer 2

You loop until the length of the list – 1 to avoid out of range:

lst = [6, 63, 131, 182, 507, 659, 669]

pairs = []
for i in range(len(lst)-1):
    pairs.append((lst[i]+1, lst[i+1]))

Answered By: kalzso

Answer 3

Consider using zip instead. This frees you from worrying about list indices (for the most part).

lst = [6, 63, 131, 182, 507, 659, 669]

for x, y in zip(lst, lst[1:]):
    print(x+1, y)

If you don’t like the idea of making a shallow copy of lst, use itertools.islice instead.

from itertools import islice


lst = [6, 63, 131, 182, 507, 659, 669]

for x, y in zip(lst, islice(lst, 1, None)):
    print(x+1, y)

Or, use itertools.pairwise, introduced in Python 3.10

for x, y in pairwise(lst):
    print(x+1, y)

Answered By: chepner

Answer 4

nums = [6, 63, 131, 182, 507, 659, 669]
pairs = [(nums[i] + 1, nums[i + 1]) for i in range(len(nums) - 1)]

You could do this in a list comprehension and stop the loop at len(nums) - 1 instead of len(nums). You probably don’t want to call a variable list because that’s a special word in python.

Answered By: Tom Wagg

Answer 5

Use slicing, and it returns everything of the message but the last element ie :-1

list = [6, 63, 131, 182, 507, 659, 669]
line_num = 0
for idx,i in enumerate(list[:-1]):
    print(list[idx]+1,list[idx+1])

Answered By: Ashok

List of tuples from original list

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