A dictionary is a collection of ordered key-value pair items.
The values can be of any type: strings, numbers, dictionaries, lists, objects, ...

Use braces ({}) to create a dictionary.
Use commas to separate items in the dictionary.

Empty dictionary: x = {} print(type(x)) # ==> <class 'dict'> print(x) # ==> {}
A dictionary with one key-value pair: x = { 'a': 1 } print(x) # ==> {'a': 1}
A dictionary with multiple key-value pairs: x = { 'a': 1, 'b': 2 } print(x) # ==> {'a': 1, 'b': 2}
Accessing keys in a Dictionary: print(x['a']) # ==> 1
Accessing a key that doesn't exist throws an error: print(x['d']) # ==> KeyError: 'd'
Using the get function (return default/custom value if the key doesn't exist): print(x.get('a')) # ==> 1 print(x.get('d')) # ==> None print(x.get('d','key not found')) # ==> key not found
Adding new key-value pairs: x['c'] = 3 x['d'] = 4 print(x) # ==> {'a': 1, 'b': 2, 'c': 3, 'd': 4}
Modifying values in a dictionary: x['a'] = 0 print(x['a']) # ==> 0
Removing key-value pairs: del x['d'] print(x) # ==> {'a': 0, 'b': 2, 'c': 3}
Looping through all key-value pairs: for key, value in x.items(): print(f'key:{key} | value:{value}') key:a | value:0 key:b | value:2 key:c | value:3
Looping through all the keys in a dictionary: for key in x.keys(): print(f'key:{key} | value:{x[key]}') print() for key in x: # calling keys() function is similar to looping on the dictionary itself print(f'key:{key} | value:{x[key]}') key:a | value:0 key:b | value:2 key:c | value:3 key:a | value:0 key:b | value:2 key:c | value:3
Looping through all the keys in a dictionary in a particular order: for key in sorted(x.keys(), reverse=True): print(f'key:{key} | value:{x[key]}') key:c | value:3 key:b | value:2 key:a | value:0
Looping through all the values in a dictionary: for value in x.values(): print(f'value:{value}') value:0 value:2 value:3
Looping through all the unique values in a dictionary: x = { 'a': 1, 'b': 2, 'c': 2 } for value in set(x.values()): print(f'value:{value}') value:1 value:2
List of dictionaries: x = { 'a': 1, 'b': 2 } y = { 'c': 2, 'd': 3 } z = [x, y] # ==> list of dictionaries #w = {x, y} # ==> set of dictionaries: TypeError: unhashable type: 'dict' d = { 'r': x, 's': y, 't': z } # ==> dictionary of list, set, and dictionaries print(x) # ==> {'a': 1, 'b': 2} print(y) # ==> {'c': 2, 'd': 3} print(z) # ==> [{'a': 1, 'b': 2}, {'c': 2, 'd': 3}] print(d) # ==> {'r': {'a': 1, 'b': 2}, 's': {'c': 2, 'd': 3}, 't': [{'a': 1, 'b': 2}, {'c': 2, 'd': 3}]}