dictionaries.py

#Using python to manipulate dictionary

'''
Python knows a number of compound data types, 
used to group together other values. One of the
most used is a dictionary
Others include:
tuple
list
set

Dictionaries are used to store data values in key:value pairs.

some_dict = {
    'a_key': 'a_value',
    'a_key_2': 'a_value_2',
    'a_key_3': ['a_list', 'as', 'a value'],
    'a_key_4': {'a_dict': 'as a value'}
}

Dictionaries are mutable - this means that item values can be changed

Dictionaries have a bunch of methods available.
clear() Removes all the elements from the dictionary
copy() Returns a copy of the dictionary
fromkeys() Returns a dictionary with the specified keys and value
get() Returns the value of the specified key
items() Returns a list containing a tuple for each key value pair
keys() Returns a list containing the dictionary's keys
pop() Removes the element with the specified key
popitem() Removes the last inserted key-value pair
setdefault() Returns the value of the specified key. If the key does not exist: 
insert the key, with the specified value
update() Updates the dictionary with the specified key-value pairs
values() Returns a list of all the values in the dictionary
'''

#The basics
some_dict = {
    'a_key': 'a_value',
    'a_key_2': 'a_value_2',
    'a_key_3': ['a_list', 'as', 'a value'],
    'a_key_4': {'a_dict': 'as a value'}
}
some_dict


some_dict[0]  # this will return an error as you need to ref the key by name
some_dict['a_key']
some_dict['a_key_4']


#Create a dict copy
some_dict.copy()

#altering a dict
some_dict['a_key'] = 'new_value'  
some_dict['a_key']

#Length
len(some_dict)

#show all keys and values
some_dict.keys()
some_dict.values()


#Dict comprehension
{x: x**2 for x in (2, 4, 6)}

#built-in function dict()
x = dict(a=1, b=2, c=3, d=4)# creates a dictionary object
x