formatting string in python with class members

Question

Consider this code:

class Foo:
  def geta(self):
    self.a = 'lie'
    return 'this is {self.a}'.format(?)

What should I write instead of the question mark so that the string will be formatted correctly?

ok, but assume I would like to have the variable name inside my string? — whomaniac
– whomaniac, Commented Feb 4, 2014 at 13:30

glglgl · Accepted Answer · 2018-07-27 10:22:05Z

16

What you probably are looking for is

'this is {0.a}'.format(self)
'this is {.a}'.format(self)
'this is {o.a}'.format(o=self)
'this is {self.a}'.format(self=self)

Note, however, that you are missing at least a method in your class.

Directly under the class scope there is no such thing as self.

edited Jul 27, 2018 at 10:22

answered Feb 4, 2014 at 13:32

glglgl

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2 Comments

tssch Over a year ago

It is best to explicitly address the referenced object with {0.a} or similar. {.a} works only once. It fails otherwise like in: "'this is {.a}, i repeat myself {.a}'.format(self)'".

glglgl Over a year ago

@tssch But if you do this is {.a}, i repeat myself {.a}'.format(self, self), it works. The first self is for the first {.a}, the second one for the second one. As documented.

Cilyan · Accepted Answer · 2014-02-04 14:20:33Z

4

The reference you include inside the brackets refers to either a number indicating the index of the argument passed to format, or a name directing to a named argument in the format call. Like that:

class Foo:
  def geta(self):
    self.a = 'lie'
    return 'this is {self.a}'.format(self=self)

edited Feb 4, 2014 at 14:20

answered Feb 4, 2014 at 13:30

Cilyan

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2 Comments

lanzz Over a year ago

This is the correct answer; just fix your code example to actually include a method definition, as OP's example is broken.

whomaniac Over a year ago

hmm, what about using something like format(self.__dict__) or something along those lines so one could easily format with all class members?

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