How to fill a tuple with a for loop

Question

I am trying to fill a tuple with named tuples using a for loop.

The example code below works:

import collections

Experiment = collections.namedtuple('Experiment', ['parameter', ])

nsize = 3

parameters = {}
for n in range(0, nsize):
    parameters[n] = n +1
   

experiments = (
        Experiment(parameter = parameters[0]),   
        Experiment(parameter = parameters[1]),
        Experiment(parameter = parameters[2]),)

However, I would like to replace the last section with a for loop:

for n in range(0, nsize):
    experiments[n] = Experiment(parameter = parameters[n])

Which gives the error:

TypeError: 'tuple' object does not support item assignment

Any ideas?

Aren't tuples immutable? In that case, it makes sense that you can't change it. — M-Chen-3
– M-Chen-3, Commented Dec 8, 2020 at 16:36
If the indices of parameters really is just a set of continuous integers from 0 to nsize - 1, consider using a list instead. parameters = list(range(1,nsize+1)). Then Mark Meyer's answer becomes simply tuple(Experiment(x) for x in parameters). — chepner
– chepner, Commented Dec 8, 2020 at 16:47
Does this answer your question? How to fix a : TypeError 'tuple' object does not support item assignment — Tomerikoo
– Tomerikoo, Commented Dec 8, 2020 at 16:52

Mark · Accepted Answer · 2020-12-08 16:40:45Z

5

Tuples are immutable, so you can't modify them after creating them. If you need to modify the data structure, you'll need to use a list.

However, instead of using a for loop, you can pass a generator expression to tuple() and make the tuple all at once. This will give you both the tuple you want and a way to make it cleanly.

import collections

Experiment = collections.namedtuple('Experiment', ['parameter', ])

nsize = 3

parameters = {}
for n in range(0, nsize):
    parameters[n] = n + 1
    
expirements = tuple(Experiment(parameter = parameters[n]) for n in range(nsize))
# (Experiment(parameter=1), Experiment(parameter=2), Experiment(parameter=3))

answered Dec 8, 2020 at 16:40

Mark

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1 Comment

coccolith Over a year ago

This works great, thanks for the super quick reply!

sdtbone · Accepted Answer · 2020-12-08 16:38:52Z

0

Tuple are immutable, you should consider changing it to a list.

answered Dec 8, 2020 at 16:38

sdtbone

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Comments

Just don't be user123 · Accepted Answer · 2020-12-08 16:45:28Z

0

Since tuples are immutable, you can convert tuples to something mutable, do you stuff and then convert it back to tuples using tuple () function

answered Dec 8, 2020 at 16:45

Just don't be user123

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