CS1-FULL-FALL2021
CS1
Week 11
Dictionaries
Maíra Marques Samary
maira.
Dictionaries
Basically it represents a collection of
something.
Dictionaries
• Dictionaries are data structures in Python that can be
understood as the generalization of lists, although there is a
fundamental difference:
• With lists we use indexes (whole numbers) to refer (and
access) to the elements. With indexes we can have a
sequential relation between the elements, that is, the
element 0 is the first and the n-1 the last.
• With a dictionary, any object can act as an index; not
necessarily an integer. Then, the “indexes” in a dictionary
are not necessarily comparable, so a sequential
relationship does not make sense.
Dictionaries
• What the dictionary keeps are associations, pairs of the
type
a list
• In addition, the keys are unique! They do not repeat.
Dictionaries in Python works
with a similar logic as the
normal dictionaries
H
Empty dictionary
What this code prints?
If we want we can evaluate if a key
exists in a dictionary with the word in
How to put a new key to my dictionary?
DictionaryName[key] = value
dn2[’trumpet’] = ’brass musical instrument’
How to get all the keys
from a dictionary
for
If we want to print the items
inside the dictionary