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

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


Is this good for you?

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


To unpack a dictionary into keyword arguments, use **. Also,, new-style formatting supports referring to attributes of objects and items of mappings:

'{0[latitude]} {0[longitude]}'.format(geopoint)'The title is {0.title}s'.format(a) # the a from your first example


As Python 3.0 and 3.1 are EOL'ed and no one uses them, you can and should use str.format_map(mapping) (Python 3.2+):

Similar to str.format(**mapping), except that mapping is used directly and not copied to a dict. This is useful if for example mapping is a dict subclass.

What this means is that you can use for example a defaultdict that would set (and return) a default value for keys that are missing:

>>> from collections import defaultdict>>> vals = defaultdict(lambda: '<unset>', {'bar': 'baz'})>>> 'foo is {foo} and bar is {bar}'.format_map(vals)'foo is <unset> and bar is baz'

Even if the mapping provided is a dict, not a subclass, this would probably still be slightly faster.

The difference is not big though, given

>>> d = dict(foo='x', bar='y', baz='z')

then

>>> 'foo is {foo}, bar is {bar} and baz is {baz}'.format_map(d)

is about 10 ns (2 %) faster than

>>> 'foo is {foo}, bar is {bar} and baz is {baz}'.format(**d)

on my Python 3.4.3. The difference would probably be larger as more keys are in the dictionary, and


Note that the format language is much more flexible than that though; they can contain indexed expressions, attribute accesses and so on, so you can format a whole object, or 2 of them:

>>> p1 = {'latitude':41.123,'longitude':71.091}>>> p2 = {'latitude':56.456,'longitude':23.456}>>> '{0[latitude]} {0[longitude]} - {1[latitude]} {1[longitude]}'.format(p1, p2)'41.123 71.091 - 56.456 23.456'

Starting from 3.6 you can use the interpolated strings too:

>>> f'lat:{p1["latitude"]} lng:{p1["longitude"]}''lat:41.123 lng:71.091'

You just need to remember to use the other quote characters within the nested quotes. Another upside of this approach is that it is much faster than calling a formatting method.


matomo