Mapping over values in a python dictionary Mapping over values in a python dictionary python python

Mapping over values in a python dictionary


There is no such function; the easiest way to do this is to use a dict comprehension:

my_dictionary = {k: f(v) for k, v in my_dictionary.items()}

In python 2.7, use the .iteritems() method instead of .items() to save memory. The dict comprehension syntax wasn't introduced until python 2.7.

Note that there is no such method on lists either; you'd have to use a list comprehension or the map() function.

As such, you could use the map() function for processing your dict as well:

my_dictionary = dict(map(lambda kv: (kv[0], f(kv[1])), my_dictionary.iteritems()))

but that's not that readable, really.


These toolz are great for this kind of simple yet repetitive logic.

http://toolz.readthedocs.org/en/latest/api.html#toolz.dicttoolz.valmap

Gets you right where you want to be.

import toolzdef f(x):  return x+1toolz.valmap(f, my_list)


You can do this in-place, rather than create a new dict, which may be preferable for large dictionaries (if you do not need a copy).

def mutate_dict(f,d):    for k, v in d.iteritems():        d[k] = f(v)my_dictionary = {'a':1, 'b':2}mutate_dict(lambda x: x+1, my_dictionary)

results in my_dictionary containing:

{'a': 2, 'b': 3}


matomo