Boston Python Workshop 8/Friday/Lists

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Defining lists

>>> your_list = ["a", "b", "c"]
>>> type(your_list)
<type 'list'>
>>> my_list = [.1, 5, -7, 15]

Length

>>> len(your_list)
3
>>> len(my_list)
4

Containment

>>> "a" in your_list
True
>>> "z" in your_list
False
>>> .5 not in my_list
True

Accessing individual elements

>>> your_list[0]
'a'
>>> your_list[1]
'b'
>>> your_list[2]
'c'
>>> your_list[3]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range
>>> your_list
['a', 'b', 'c']

Appending elements

>>> your_list.append("d")
>>> len(your_list)
>>> your_list[3]
'd'

How would we create an empty list?

>>> her_list = []
>>> len(her_list)
0

replacing elements (band example)

>>> names = ["Alice", "Amy"]
>>> names.append("Adam")
>>> names
['Alice', 'Amy', 'Adam']
>>> names[0] = "Jimmy" # not cutting it on drums
>>> names
['Jimmy', 'Amy', 'Adam']
>>> names[2] = "Rachel" # too much time with groups
>>> names
['Jimmy', 'Amy', 'Rachel']

Remember:

= is for assignment
== is for comparison

>>> names.append("Tim") # sax
>>> names.append("Bob") # trumpet
>>> names.append("Alexis") # french horn
>>> names
['Jimmy', 'Amy', 'Rachel', 'Tim', 'Bob', 'Alexis']
>>> len(names)
6

how do you get elements off the end of a list? Use negative numbers!

>>> names[-1]
'Alexis'
>>> names[-2]
'Bob'
>>> names[-3]
'Tim'

lists and strings are similar
- length
- stuff in an order

>>> my_name[0]
'J'
>>> my_name[-1]
'a'

Review

>>> fruits = ["apples", "bananas", "oranges"]
>>> fruits[0]
'apples'
>>> fruits[-1]
'oranges'
>>> fruits[0] = "plums"
>>> fruits.append("cherries")
>>> fruits
['plums', 'bananas', 'oranges', 'cherries']
>>> len(fruits)
4
>>> "apples" in fruits
False
>>> "cherries" in fruits
True