Mass producing variables using eval - python

Question

I want to produce about 100 variables, each assigned to its own integer So for example, number_1=1,number_2=2,number_3=3 etc.. I have tried to use eval in the following way:

for x in range(1,101):
   eval('number_'+str(x)) = x

I receive the error 'cant assign to function call'. I've also tried:

for x in range(1,101):
   eval(('number_'+str(x)) = x)

Which gives the error 'keyword can't be an expression' Is there a way to do this? I am aware of the risks associated with eval and exec, but there is no user input or internet access in my code. Thanks!

Edit: This isn't the same as the other thread suggested, since here I'm trying to alter the name of the variable as well as its value.

Possible duplicate of How can I assign the value of a variable using eval in python? — bunji
– bunji, Commented May 2, 2017 at 19:48
I'm trying to create a moving average of readings from a raspberry pi. I'm sure there are more efficient ways of doing it, but I've wanted to create variables in this way before so I thought I'd ask anyway. — JoeP
– JoeP, Commented May 2, 2017 at 19:57
Use a list. You only think you want to create variables dynamically because you haven't gotten used to using actual data structures yet. — user2357112
– user2357112, Commented May 2, 2017 at 20:02

Maximilian Peters · Accepted Answer · 2017-05-02 20:07:32Z

-1

You could use exec.

for i in range(100):
    exec('number_{0} = {0}'.format(i))

edited May 2, 2017 at 20:07

answered May 2, 2017 at 19:47

Maximilian Peters

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5 Comments

user2357112 Over a year ago

The special-case handling they used in the code generator to make this work in Python 2 went away in Python 3, so this fails on Python 3.

Maximilian Peters Over a year ago

@user2357112: tested it with python 3.6, see screenshot in answer.

user2357112 Over a year ago

You tested it outside of a function. It only works outside of a function, and "avoid writing functions" is not a lesson we should be teaching people.

Maximilian Peters Over a year ago

@user2357112: I agree with you that it is not a good idea to declare variables outside a function but the question was not 'what is the best way?' but how to do it with eval and exec.

JoeP Over a year ago

I've just tested it in my code - apparently it doesn't work in python 3 but does in 2. I don't really mind using 2, since my RPi loads it in python 2 automatically. I'd still rather a python 3 solution though

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