How to create a dictionary in python

python dictionary definition

Dictionary is another mutable container model and can store any type of object.

Each key-value key=>value pair in the dictionary is separated by colon :. Each key-value pair is separated by comma,. The entire dictionary is included in curly braces {}. The format is as follows:

d = {key1 : value1, key2 : value2 }

The key is generally unique. If the last key-value pair is repeated, the previous one will be replaced. The value does not need to be unique.

>>>dict = {'a': 1, 'b': 2, 'b': '3'}
>>> dict['b']
'3'
>>> dict
{'a': 1, 'b': '3'}

Other common ways to create a dictionary in Python:

Dynamic assignment of key values

>>> d ={}
>>> d['name'] = 'Allen'
>>> d
{'name': 'Allen'}

If needed This method is more appropriate if you dynamically create one field of a dictionary at a time.

Dictionary key-value table

>>> c = dict(name='Allen', age=14, gender='male')
>>> c
{'gender': 'male', 'age': 14, 'name': 'Allen'}

Because this form has simple syntax and is less error-prone, it is very popular.

This form requires less code than constants, but the keys must all be strings, so the following code will report an error:

>>> c = dict(name='Allen', age=14, gender='male', 1='abcd')
  File "", line 1
SyntaxError: keyword can't be an expression

Dictionary key value tuple table

>>> e=dict([('name','Allen'),('age',21),('gender','male')])
>>>
>>>
>>> e
{'gender': 'male', 'age': 21, 'name': 'Allen'}

This method is useful if you need to gradually build the keys and values ​​into a sequence while the program is running.

The values ​​of all keys are the same or assigned initial values

>>> f=dict.fromkeys(['height','weight'],'normal')>>> f
{'weight': 'normal', 'height': 'normal'}

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