Lists and tuples

tuple = list that can’t be modified*

Create an empty list

my_list = []

Create a populated list

my_list = [1, 3.5, "une chaine", []]

Access a list element

elt = my_list[3]

Insert an element at the end of the list : append

my_list.append(56)      # Add 56 at the end of the list

Insert an element at a specific index : insert

my_list = ['a', 'b', 'd', 'e']
my_list.insert(2, 'c')         # -> ['a', 'b', 'c', 'd', 'e']

Remove an element from a list

• By index : keyword del

my_list = [-5, -2, 1, 4, 7, 10]
del my_list[0]
# -> [-2, 1, 4, 7, 10]
del ma_liste[2]
# -> [-2, 1, 7, 10]

• By content : method remove

my_list = [31, 32, 33, 34, 35]
my_list.remove(32)
# -> [31, 33, 34, 35] (removes the element that contains '32')

Clear list

my_list.clear()

Returns a list of coupled values containing the list index with its associated element : enumerate()

Example :

ma_liste = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']

for i, elt in enumerate(ma_liste):
    print("À l'indice", i, "se trouve", elt)

-> output :

À l'indice 0 se trouve a.
À l'indice 1 se trouve b.
À l'indice 2 se trouve c.
À l'indice 3 se trouve d.
À l'indice 4 se trouve e.
À l'indice 5 se trouve f.
À l'indice 6 se trouve g.
À l'indice 7 se trouve h.

Use lists as function parameters

Place a * in front of the parameter which takes a list, or use ... :

def fonction(*parametres):
    ...

def print(*values, sep=' ', end='\n', file=sys.stdout):
    ...
# Is equivalent to :
def print(value, ..., sep=' ', end='\n', file=sys.stdout)
    ...

List Comprehensions : a concise way to create lists

It’s a concise way to create a list. For example :

new_list = []
for i in old_list:
    if filter(i):
        new_list.append(expressions(i))

… is equivalent to :

new_list = [expression(i) for i in old_list if filter(i)]