Different forms of dict() constructors are:
class dict(**kwarg) class dict(mapping, **kwarg) class dict(iterable, **kwarg)
Note: **kwarg let you take an arbitrary number of keyword arguments.
A keyword argument is an argument preceded by an identifier (eg. name=). Hence, the keyword argument of the form kwarg=value is passed to dict() constructor to create dictionaries.
dict() doesn't return any value (returns None).
Example 1: Create Dictionary Using keyword arguments only
numbers = dict(x=5, y=0)
print('numbers =', numbers)
print(type(numbers))
empty = dict()
print('empty =', empty)
print(type(empty))
Output
numbers = {'y': 0, 'x': 5}
<class 'dict'>
empty = {}
<class 'dict'>
Example 2: Create Dictionary Using Iterable
# keyword argument is not passed
numbers1 = dict([('x', 5), ('y', -5)])
print('numbers1 =',numbers1)
# keyword argument is also passed
numbers2 = dict([('x', 5), ('y', -5)], z=8)
print('numbers2 =',numbers2)
# zip() creates an iterable in Python 3
numbers3 = dict(zip(['x', 'y', 'z'], [1, 2, 3]))
print('numbers3 =',numbers3)
Output
numbers1 = {'y': -5, 'x': 5}
numbers2 = {'z': 8, 'y': -5, 'x': 5}
numbers3 = {'z': 3, 'y': 2, 'x': 1}
Example 3: Create Dictionary Using Mapping
numbers1 = dict({'x': 4, 'y': 5})
print('numbers1 =',numbers1)
# you don't need to use dict() in above code
numbers2 = {'x': 4, 'y': 5}
print('numbers2 =',numbers2)
# keyword argument is also passed
numbers3 = dict({'x': 4, 'y': 5}, z=8)
print('numbers3 =',numbers3)
Output
numbers1 = {'x': 4, 'y': 5}
numbers2 = {'x': 4, 'y': 5}
numbers3 = {'x': 4, 'z': 8, 'y': 5}
Recommended Reading: Python dictionary.