Python Lists

Return a single item

Return the item at a specific index. Negative integers count back from the last item in the list.

my_list = ["Nick", "Jess", "Schmidt", "Winston"]
my_list[2]  # Schmidt
my_list[-1] # Winston (-1 always returns the last item)

Return the first item that satisfies the provided predicate.

my_list = ["Nick", "Jess", "Schmidt", "Winston", "Winnie"]
next((item for item in my_list if item.startswith("Wins")), None) # Winston

Return a new list

Returns a new list with the results of calling a provided function on every item in the list.

my_list = ["Nick", "Jess", "Schmidt", "Winston"]
my_upper_list = [item.upper() for item in my_list] # ["NICK", "JESS", "SCHMIDT", "WINSTON"]

Returns a new, filtered list with all items that satisfy the condition.

my_list = ["Nick", "Jess", "Schmidt", "Winston"]
my_filtered_list = [item for item in my_list if len(item) > 4] # ["Schmidt", "Winston"]

Merges two or more lists or values into a single list and returns it.

my_list_1 = ["Nick", "Jess", "Schmidt", "Winston"]
my_list_2 = ["Cici", "Coach"]

# `+` operator
final_list = my_list_1 + my_list_2    # ["Nick", "Jess", "Schmidt", "Winston", "Cici", "Coach"]

# Extend (mutates `my_list_1` in place)
my_list_1 += my_list_2                # ["Nick", "Jess", "Schmidt", "Winston", "Cici", "Coach"]
my_list_1.extend(my_list_2)           # same thing

# Unpacking (similar to JS spread operator(...))
final_list = [*my_list_1, *my_list_2] # ["Nick", "Jess", "Schmidt", "Winston", "Cici", "Coach"]

Return a sorted list.

my_list = [3,1,2,6,4,5]
sorted(list, reverse=True) # [6, 5, 4, 3, 2, 1]

Return a string

Concatenates all items in the list into a single string.

my_list = ["Nick", "Jess", "Schmidt", "Winston"]
no_delimeter = "".join(my_list)    # "NickJessSchmidtWinston"
dash_delimited = "-".join(my_list) # "Nick-Jess-Schmidt-Winston"

Return a boolean

Returns a boolean value for an item’s presence in a list.

my_list = ["Nick", "Jess", "Schmidt", "Winston"]
"Winston" in my_list # True
"Coach" in my_list   # False

Returns True if at least one item in the list passes the condition.

my_list = ["Nick", "Jess", "Schmidt", "Winston"]
any(item.startswith("J") for item in my_list) # True

Returns True if every item in the list passes the condition.

my_list = ["Nick", "Jess", "Schmidt", "Winston"]
all(len(item) > 3 for item in my_list) # True

Modifying lists

Add a new item at the end.

my_list = [1,2,3]
my_list.append(4) # [1, 2, 3, 4]

Insert an item at a specific index.

my_list = [1,2,3]
my_list.insert(0, 99) # [99, 1, 2, 3]

Remove a particular item.

my_list = [1,2,3]
my_list.remove(3) # [1, 2]