Python Print Variables with parameters

Question

I know you can do this for a string:

print("You have inputted {0} postive numbers and {1} negative numbers".format('3','2'))

And this would produce:

You have inputted 3 postive numbers and 2 negative numbers

But I want to insert a letter in a variable name. For example,

number = 4
print(nu{}ber.format("m"))

And this should produce 4 Any ideas?

Dmitry Torba · Accepted Answer · 2016-08-25 18:08:49Z

2

print(eval('nu{}ber'.format("m")))

Eval evaluates the expression from string, and has access to program variables by default.

Or:

print(globals()['nu{}ber'.format("m")])

Globals is the dictionary {'variable_name': value}.

Unless you do trust the source of the string though, you should be careful. Fore example, if you have

class Nuke:
    def destroy_everything():
        launch_nukes()

class Cucumber:
    ...

print(eval('nu{}ber'.format(string_received_from_user)))

And

string_received_from_user = "ke.destroy_everything() or Cucum"

Than the command

Nuke.destroy_everything() or Cucumber

will be executed.

answered Aug 25, 2016 at 17:59

Dmitry Torba

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Comments

kjaquier · Accepted Answer · 2016-08-25 18:00:57Z

0

Though it's not recommended, you can access your variable dynamically through globals:

>>> number = 4
>>> globals()['num' + 'ber']
4

eval works too:

>>> eval('num' + 'ber')
4

answered Aug 25, 2016 at 18:00

kjaquier

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