Dictionaries 30/03
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# Dictionary
# dict - data type but also data structure, a way to organise data
# #dictionary = {
# 'a': 1,
# 'b': 2
# }
# print(dictionary['b']) # will go to b and grab the value, 2
# unordered key:value pair - in larger amounts the data may not be ordered as expected - ordered now in 3.7
# dictionary = {
# 'a': [1,2,3],
# 'b': 'hello',
# 'x': True
# }
# print(dictionary['b'])
# list vs dictionary - lists tend to be sorted, dict less often
# dictionaries can hold more information, while a list has the index and value only
# dictionary holds keys and values, leading to more info available to store/hold
# Dictionary Keys
# Dictionary keys require special property - Immutability
# For example, a number/string is acceptable, but a list is not as it can be changed
# Most of the time a key for a dictionary will be descriptive
# a key in a dictionary must be unique - repeated versions of a key will overwrite with new data
# e.g. two values with a key of '123' will prioritize the second version for an action like print
# Dictionary Methods
user = {
'basket': [1,2,3],
'greet': 'hello',
'age': 20
}
# print(user.get('age')) #user.get is a method to find if the value exists in the dictionary, here we get "None" returned
# # this saves from errors occuring and stopping processes
# user2 = dict(name= 'JohnJohn')# basic form of creating a dictionary but not very common
# print(user.get('age', 55)) # by adding a value after the key, this provides a "default" answer to output if none exists
# print(user2) # prints the user2 dictionary
# print('goop' in user) # in checks if a key is within a variable, True or False
# print(20 in user.values())# user.keys and user.values allow to check if exists in those regions
# print(user.items()) # this will print the entire set of items in the dictionary for the variable
# print(user.clear()) # prints an empty dictionary - clear removes all items from dictionary
# user2 = user.copy() # duplicates the dictionaries
# print(user.clear()) # this will only clear the first user data, leaving user 2 with the original data
# print(user2)
# print(user.pop('age')) # returns value of whatever has been removed
# print(user) # the value will not be present when printing
# popitem - will remove the last key:value pair inserted in dictionary as of 3.7
# print(user.update({'age': 55})) # simply updates the value of the key, or adds a new key if not previously existing
# print(user)
Python
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