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Dictionaries

Dictionaries are a data structure made up of 'keys' and 'values' created with the use of curly-braces '{}' in Python.

Rules:

  • Keys must be unique.
  • If a Key needs more than 1 Value, you must use a list, nested dictionary, tuple or other iterable.

Create a Dictionary

Before you can replace, update or delete any keys or values you must instantiate the dictionary.

Empty dictionary:

my_dict = {}

Or instantiate with keys and values:

my_dict = {'key1': 'value1'}
or
my_dict['key1'] = 'value1'

You can call the object directly or print the dictionary:

>>> my_dict = {'key1': 'value1'}

>>> my_dict
{'key1': 'value1'}

Using print():

>>> my_dict = {'key1': 'value1'}

>>> print(my_dict)
{'key1': 'value1'}

Add Key & Value to Existing Dictionary

  • Key must be unique
  • If Key is not unique Value will be overwritten.

Start with a dictionary

>>> my_dict = {'key1': 'value1'}
>>> my_dict
{'key1': 'value1'}

Create a new Key with Value

>>> my_dict['key2'] = 'value0'
>>> my_dict
{'key1': 'value1', 'key2': 'value0'}

Update the Value for existing Key (overwrite)

>>> my_dict['key2'] = 'value1'
>>> my_dict
{'key1': 'value1', 'key2': 'value1'}

Add multiple Values to Key

Because a Value is a single object, I commonly use list's when I need a Key to contain multiple Values.

Convert your Key with a single value to a Key with a list object as a Value:

>>> my_dict['key1'] = [my_dict['key1']]
>>> my_dict
{'key1': ['value1']}