Fix Python – How do I format a string using a dictionary in python-3.x?

Question

Asked By – Doran

I am a big fan of using dictionaries to format strings. It helps me read the string format I am using as well as let me take advantage of existing dictionaries. For example:

class MyClass:
    def __init__(self):
        self.title = 'Title'

a = MyClass()
print 'The title is %(title)s' % a.__dict__

path = '/path/to/a/file'
print 'You put your file here: %(path)s' % locals()

However I cannot figure out the python 3.x syntax for doing the same (or if that is even possible). I would like to do the following

# Fails, KeyError 'latitude'
geopoint = {'latitude':41.123,'longitude':71.091}
print '{latitude} {longitude}'.format(geopoint)

# Succeeds
print '{latitude} {longitude}'.format(latitude=41.123,longitude=71.091)

Now we will see solution for issue: How do I format a string using a dictionary in python-3.x?


Answer

Since the question is specific to Python 3, here’s using the new f-string syntax, available since Python 3.6:

>>> geopoint = {'latitude':41.123,'longitude':71.091}
>>> print(f'{geopoint["latitude"]} {geopoint["longitude"]}')
41.123 71.091

Note the outer single quotes and inner double quotes (you could also do it the other way around).

This question is answered By – Wyrmwood

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