[SOLVED] How to fill a tuple with a for loop

How to fill a tuple with a for loop

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?

Solution

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))