""" Purpose: introduce the dict type
"""

# initialize dictionary and print it out
flora_to_color = { 'spruce': 'green',     'apple': 'red',       'shamrock': 'green',
                   'banana': 'yellow',    'potato': 'brown',    'eggplant': 'purple' }

print( "flora_to_color: ", flora_to_color )

print(); input( "Enter when ready. " ); print()

# determine number of mappings
nbr_mappings = len( flora_to_color )
# using the len() function will give you how many mappings there are in the dictionary - keys are unique, values are not
# should be the number of colons when you print the dict

print( "len( flora_to_color): ", nbr_mappings )

print(); input( "Enter when ready. " ); print()

# access individual dictionary entry
c1 = flora_to_color[ 'potato' ] # use [] to access value associated with a key in the dictionary
# this will not change the dictionary, because the dictionary is on the right of the assignment operator ( = )
# only c1 is changed in this
# **this will ONLY work to access the value associated with a key. you can't search by value in this way
print( "flora_to_color[ 'potato' ]: )", c1 )

print(); input( "Enter when ready. " ); print() # this is to break up the output so we can talk about what's happening

# add mapping to dictionary
flora_to_color[ 'lemon' ] = 'yellow'
# creates a new mapping with 'lemon' as the key mapping to the value 'yellow'
# this works becaue 'lemon' has not been used as a key in the dict
# this won't necessarily go to the "end" of the dictionary, because there is no end to it
# with lists, we had order because elements were indexed by their position
# in a dict, we don't have order because values are mapped to keys - there is no "first" element in a dictionary
# data structures can be dynamic, so if you search something often it will keep that information close and easy to find
# dict[ key ] = value
    # if key is already in the dictionary, this will overwrite the mapping and update it
    # if the key is not already in the dictionary, this will add a new mapping of the key to the value
print( "flora_to_color: ", flora_to_color )

print(); input( "Enter when ready. " ); print()

# reset dictionary mapping
flora_to_color[ 'potato' ] = 'golden'
# each key is unique, so because 'potato' was already used as a key, we lose the old mapping to 'brown' and replace
# it with a new mapping to 'golden'
# dictionaries are like lists that use keys instead of indices to locate values
print( "flora_to_color: ", flora_to_color )
# print( "c1:", c1 ) c1 is still 'brown', because that is what 'potato' mapped to when c1 was assigned above

print(); input( "Enter when ready. " ); print()

# get the keys and values of the dictionary --> dictionary functions!
flora_keys = flora_to_color.keys() # this hands back a special sequence ( dict_keys ) containing all of the keys ( unordered! )
color_values = flora_to_color.values() # this hands back a special sequence called dict_values of all of the values
# not all built-in functions will work with dict_keys or dict_values because they aren't quite lists
print( "flora_to_color.keys(): ", flora_keys )
print( "flora_to_color.values(): ", color_values )

print(); input( "Enter when ready. " ); print()

# convert keys and values to lists
flora = list( flora_keys ) # we can use the list() function to cast our dict_keys into a list
colors = list( color_values ) # use list() to cast dict_values to a list
# any built-in function that works on a list will work on our flora and colors lists
print( "list( flora_to_color.keys() ): ", flora )
print( "list( flora_to_color.values() ): ", colors )

print(); input( "Enter when ready. " ); print()

# loop through the mappings

for key in flora_to_color: # key is our loop variable. what would that indicate that we're looping through?
    # **when you loop through a dict in a for loop, your loop variable will take on each key value**
    value = flora_to_color[ key ] # find the value using the key
    print( key, ":", value )
flora_to_color[ 'potato' ] = [ 'red', 'yellow', 'golden', 'brown', 'purple' ]
print( "flora_to_color:", flora_to_color )
# notes:
    # number of keys = number of values = len( dict )
    # keys must be unique, values can be repeated
    # keys must map to one value. that value can be a list if you want to associate multiple values with a single key
    # in operator: key in dict
        # returns True if key is present and False if it is not

print(); input( "Enter when ready. " ); print()
c2 = flora_to_color.get( 'green' ) # val = dict.get( key )
# this will hand back None ( because 'green' is not a key ), which means there is nothing there
# .get( key ) will not result in an error like [ key ] if the key is not in the dictionary, so it is considered safer
    # how might the .get() function work?
    # try-catch blocks: try it out, look for an error and catch that error and do something else
        # try [] operator
        # catch error and hand back nothing if it does not work

print("c2:", c2 )

print(); input( "Enter when ready. " ); print()

del flora_to_color[ 'shamrock' ] # del d[ key ] will delete the mapping of that key and updates the dictionary
print( "flora_to_color:", flora_to_color )
# python variables do not remember their old values, the dictionary never knew it had a 'shamrock' mapping