Can I format a variable in python?

Question

Is there a way of formating a variable?

For example, I'd like to automate the creation of a variable named M_color, where M is a string of value "bingo". The final result would be bingo_color. What should I do if the value of M changes during the execution?

It's best not to rely on dynamic variable names. This leads to dangerous pitfalls like in PHP's $$ variable variables... Just bad. Please consider using dictionary keys as suggested by other respondents. — jathanism
– jathanism, Commented Jul 19, 2010 at 18:47

Marius Gedminas · Accepted Answer · 2010-07-19 17:56:37Z

8

The best solution for this kind of problem is to use dictionaries:

color_of = {}
M = "bingo"
color_of[M] = "red"
print(color_of[M])

answered Jul 19, 2010 at 17:56

Marius Gedminas

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Comments

Josh Wright · Accepted Answer · 2010-07-19 18:02:30Z

1

If the 'variable' can be an attribute of an object, you could use setattr()

class Color(object):
    pass

color = Color()

attr_name = '{foo}_color'.format(foo='bingo')
setattr(color, attr_name, 'red')

Beyond that, you're looking at using eval()

edited Jul 19, 2010 at 18:02

answered Jul 19, 2010 at 17:57

Josh Wright

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1 Comment

Marius Gedminas Over a year ago

You could also do globals()[attr_name] = 'red' instead of eval, but I wouldn't recommend either.

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