Unique variable names in a for loop using Python

Question

I have 10 lists and want to perform same process on all of them and like to have unique name of all variables. Here is what I have:

for i in xrange(1,11,1):
    m + str(i) = np.array(m + str(i)).astype(np.float)

It throws syntax error:

Can't assign to operator(mean.py,line30)

You can't assign to an arbitrary expression, only names (x) and indexed expressions (x[1] for lists, x['foo'] for dicts). — chepner
– chepner, Commented Oct 28, 2015 at 20:50
@Hackaholic: a variable name as I would like to save all lists with names m1, m2..... — Ibe
– Ibe, Commented Oct 28, 2015 at 20:52
Don't use multiple similarly named variables; use a single list m. — chepner
– chepner, Commented Oct 28, 2015 at 20:52
Or use a single multi-dimensional array. Depending on what your data looks like, that might be more appropriate. — user2357112
– user2357112, Commented Oct 28, 2015 at 20:56
Whenever you find yourself using sequentially numbered variables, you should probably be using an array/list instead. This is true for almost all programming languages. — Barmar
– Barmar, Commented Oct 28, 2015 at 21:02

chepner · Accepted Answer · 2015-10-28 20:53:44Z

1

Instead of m1 et al., use a single list m.

m = [ ... ]
for i in xrange(1,11,1):
    m[i] = np.array(m[i]).astype(np.float)

answered Oct 28, 2015 at 20:53

chepner

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5 Comments

Hackaholic Over a year ago

at start list m is empty, so you might get list index out of range

chepner Over a year ago

m should be created as the collection of individual variables; m = [m1, m2, m3].

chepner Over a year ago

What is list + str(i) supposed to be? If you already have m1 et al. defined, you can literally just write m = [m1, m2, m3] to create the list. Ideally, though, you get rid of those variables and define m in terms of whatever you used to set the individual variables

chepner Over a year ago

Add an example of how you set the individual variables to your question.

Ibe Over a year ago

I created m as list of lists and used above. It worked. Thanks!

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