Python - get all index from another list

Question

I`m trying to append an list of the indexes of another list.

I have one list with random numbers, and need to create another list, with the indexes of the first list.

My code is just like this:

from random import seed
from random import randint
seed(715)
g1 = []
g2 = []
for v in range(20328):
valor = randint(40, 220)
g1.append(valor)


for v in enumerate(g1):
    g2.append(v)

print("v g1[v] g2[v] g1[g2[v]]")
for v in [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]:
    print(v, g1[v], g2[v], g1[g2[v]])

But I get the error below:

print(v, g1[v], g2[v], g1[g2[v]])
TypeError: list indices must be integers or slices, not tuple

What am i doing wrong?

Because g2 list contains tuples due to enumerate.

Space Impact
– Space Impact

2018-11-06 19:19:37 +00:00
Commented Nov 6, 2018 at 19:19 — Space Impact
– Space Impact, Commented Nov 6, 2018 at 19:19

sinapan · Accepted Answer · 2018-11-06 19:34:36Z

1

g2 is set as a list of tuples in your program, not integers. If you use print(g2[0]) to see what's inside you'll get something like g2[0]:(0, 69) which is a tuple. So that's the problem.

You can use any of the following to resolve the issue:

for v in enumerate(g1):
    g2.append(v[1])

or

for index, value in enumerate(g1):
    g2.append(value)

or

for value in g1:
    g2.append(value)

Helpful resource: https://docs.python.org/3/library/functions.html#enumerate

answered Nov 6, 2018 at 19:34

sinapan

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Comments

olisch · Accepted Answer · 2018-11-06 19:23:38Z

0

you are using enumerate to fill g2 with tuples, enumarate will give you the index and the value as a tuple, so whenever you call g2[v], you won't get the index only, you will get a tuple of (index, value). If you want the index only in g2, you should use something like the following the create g2.

for i, v in enumerate(g1):
    g2.append(i)

answered Nov 6, 2018 at 19:23

olisch

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BredAndButter · Accepted Answer · 2018-11-06 19:22:55Z

0

Like Sandeep Kadapa said, g2 gets turned into a tuple, so try to do something like,

list(g2)

after the enumerate and before the print functions are called.

answered Nov 6, 2018 at 19:22

BredAndButter

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Comments

dabjaro · Accepted Answer · 2018-11-06 19:31:05Z

0

Maybe you need to add only indexes to the second list?

for index, v in enumerate(g1):
    g2.append(index)

Btw I would replace that function with something like that:

g2 = list(range(len(g1))

Let me know if it works for you

edited Nov 6, 2018 at 19:31

answered Nov 6, 2018 at 19:26

dabjaro

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Comments

Michael Lihs · Accepted Answer · 2018-11-06 19:34:36Z

0

Enumerate in your code sets v as a tuple. You produce the index and the element with the following format:

for count, v in enumerate(g1):
    g2.append(count)

where count will be the index of g1, and v will be the element at that index.

edited Nov 6, 2018 at 19:34

Michael Lihs

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answered Nov 6, 2018 at 19:26

mhoffman2016

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