# Define a tuple with parentheses colors = ('Red', 'Blue', 'Green') # Iterate over tuple with for loop for item in colors: print item # Get an item from a tuple by index print(colors) # Prints: Green # Results in a type error: tuples can't be changed once created! colors = "chartreuse"
# Convert a list to a tuple with tuple() rocky = ['Mercury', 'Venus', 'Earth', 'Mars'] rocky_tuple = tuple(rocky) # Convert a tuple to a list with list() giants = ('Jupiter', 'Saturn', 'Uranus', 'Neptune') giant_list = list(giants)
# Create a single-item tuple (comma needed after first item) one_item = ('So lonely',)
Tuples are one of Python's basic composite data types, along with lists
and dictionaries. A tuple is a lot like a list, in that it consists of a
sequence of elements that can be accessed by index. However, unlike a list,
a tuple can't be modified after it's created. (Tuples can't be assigned to
by index, nor do they have an append() method.)
You can convert a list to a tuple using the tuple() function, or convert a tuple to a list using list().
Because tuples have a fixed size, Python can make some optimizations behind the scenes regarding how they're stored in memory. For this reason, tuples can be marginally faster and more efficient than lists in some applications. Because tuples are immutable (i.e., they can't be changed after creation), they are also "hashable" and can be used as keys in dictionaries.
When writing a tuple literal that has only one element, you need to put a comma after that element. (Otherwise, Python will interpret the parentheses as "grouping" a single expression for the purposes of controlling the order of execution.)
var = (elem1, ..., elemN)
 (Index brackets)