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Python - Tuple

Python - Tuple

Tuple

Tuples: to store multiple items in a single variable.
A tuple is a collection which is ordered and unchangeable.
Tuples are written with round brackets.
Tuple Items
- Tuple items are ordered, unchangeable, and allow duplicate values.
- Tuple items are indexed, the first item has index [0], the second item has index [1] etc.
Ordered
- order will not change.
Unchangeable
- cannot change, add or remove items after the tuple has been created.
Allow Duplicates
- can have items with the same value
Tuple Length
- len() function: how many items a tuple has

Tuple Method

Method	Description
`count()`	Returns the number of times a specified value occurs in a tuple
`index()`	Searches the tuple for a specified value and returns the position of where it was found

Create a tuple

1. round brackets

tuple() Constructor

print("\n--------Create a tuple--------\n")

# round-brackets
xtuple = ("apple", "banana", "cherry")
print(xtuple)   # ('apple', 'banana', 'cherry')

# tuple() Constructor
xtuple = tuple(("apple", "banana", "cherry"))  # note the double round-brackets
print(xtuple)   # ('apple', 'banana', 'cherry')

To create a tuple with only one item, you have to add a comma after the item, otherwise Python will not recognize it as a tuple.

xtuple = ("apple",)
print(type(xtuple))  # <class 'tuple'>

# NOT a tuple
xtuple = ("apple")
print(type(xtuple))  # <class 'str'>

Tuple items can be of any data type.

tuple1 = ("apple", "banana", "cherry")  # string
tuple2 = (1, 5, 7, 9, 3)                # number
tuple3 = (True, False, False)           # boolean
tuple1 = ("abc", 34, True, 40, "male")  #  can contain different data types

type()

xtuple = ("apple", "banana", "cherry")
print(type(xtuple))     # <class 'tuple'>

Access Items

access tuple items by referring to the index number, inside square brackets

print("\n--------Access Items--------\n")
# Access Items
xtuple = ("apple", "banana", "cherry")
print(xtuple[0])  # apple
print(xtuple[1])  # banana
# print(xtuple[3])  # Error: IndexError: list index out of range

# Negative Indexing
print(xtuple[-1])  # cherry
print(xtuple[-2])  # banana

# Range of Indexes
xtuple = ("apple", "banana", "cherry", "orange", "kiwi", "melon", "mango")
print(xtuple[2:5])   # ['cherry', 'orange', 'kiwi']
print(xtuple[:5])   # exclusive ['apple', 'banana', 'cherry', 'orange', 'kiwi']
print(xtuple[5:])   # inclusive ['melon', 'mango']

# Range of Negative Indexes
xtuple = ("apple", "banana", "cherry", "orange", "kiwi", "melon", "mango")
print(xtuple[-4:-1])  # ['orange', 'kiwi', 'melon']

Change Tuple Values

Once a tuple is created, you cannot change its values. Tuples are unchangeable, or immutable as it also is called.
Change Tuple Values: can convert the tuple into a list, change the list, and convert the list back into a tuple.

xtuple = ("apple", "banana", "cherrylist")
ylist = list(xtuple)
ylist[1] = "kiwi"
xtuple = tuple(ylist)

print(xtuple)   # ('apple', 'kiwi', 'cherrylist')

Add Items

Convert into a list: tuple -> list -> tuple.
Add tuple to a tuple. create a new tuple with the item(s), and add it to the existing tuple.

xtuple = ("apple", "banana", "cherrylist")
ylist = list(xtuple)
ylist.append("kiwi")
xtuple = tuple(ylist)

print(xtuple)   # ('apple', 'banana', 'cherrylist', 'kiwi')


xtuple = ("apple", "banana", "cherry")
ylist = ("orange",)
xtuple += ylist

print(xtuple)   # ('apple', 'banana', 'cherry', 'orange')

Remove Items

Convert into a list: tuple -> list -> tuple.
delete the tuple completely

xtuple = ("apple", "banana", "cherry")
ylist = list(xtuple)
ylist.remove("apple")
xtuple = tuple(ylist)

print(xtuple)   # ('banana', 'cherry')

xtuple = ("apple", "banana", "cherry")
del xtuple
print(xtuple)  # NameError: name 'xtuple' is not defined

Unpack

unpacking: Python allowed to extract the values back into variables.
- Note: The number of variables must match the number of values in the tuple, if not, you must use an asterisk to collect the remaining values as a list.
- If the number of variables is less than the number of values, it raises ValueError: too many values to unpack.
- If the number of variables is less than the number of values, can add an * to the variable name and the values will be assigned to the variable as a list
- If the number of variables is more than the number of values, it raises ValueError: not enough values to unpack.

print("\n------Unpacking------\n")

print("\n------Equal------\n")
# number of variables must match number of items
fruits = ("apple", "banana", "cherry")
(green, yellow, red) = fruits

print(green)    # apple
print(yellow)   # banana
print(red)      # cherry

print("\n------Less than------\n")

#  if number of variables is less than number of items, Error
fruits = ("apple", "banana", "cherry")
# (green, yellow) = fruits    # ValueError: too many values to unpack (expected 2)

#  if number of variables is less than number of items, should Asterisk
fruits = ("apple", "banana", "cherry")
(green, *yellow) = fruits
print(green)    # apple
print(yellow)   # ['banana', 'cherry']


fruits = ("apple", "mango", "papaya", "pineapple", "cherry")
(green, *tropic, red) = fruits
print(green)    # apple
print(tropic)   # ['mango', 'papaya', 'pineapple']
print(red)      # cherry

print("\n------More than------\n")
fruits = ("apple", "banana", "cherry")
# ValueError: not enough values to unpack (expected 4, got 3)
(green, yellow, red, grey) = fruits

Check if Item Exists:`in`

xlist = ("apple", "banana", "cherry")
if "apple" in xlist:
    print("Yes, 'apple' is in the fruits list")

Loop Tuple

for in loop
for in range(len()) loop
while Loop

print("\n--------for in loop--------\n")
# for in loop
xtuple = ("apple", "banana", "cherry")
for x in xtuple:
    print(x)


print("\n--------for in range loop--------\n")
# for in range(len())
xtuple = ("apple", "banana", "cherry")
for i in range(len(xtuple)):     # [0, 1, 2]
    print(xtuple[i])


print("\n--------While Loop--------\n")
# While Loop
xtuple = ("apple", "banana", "cherry")
i = 0
while i < len(xtuple):   # 可以用于判断是否进入循环
    print(xtuple[i])
    i = i + 1

Join Tuple

+ operator
* operator

print("\n--------Join tuple--------\n")
tuple1 = ("a", "b", "c")
tuple2 = (1, 2, 3)

tuple3 = tuple1 + tuple2
print(tuple3)   # ('a', 'b', 'c', 1, 2, 3)


fruits = ("apple", "banana", "cherry")
mytuple = fruits * 3

# ('apple', 'banana', 'cherry', 'apple', 'banana', 'cherry', 'apple', 'banana', 'cherry')
print(mytuple)

count()

count(): Returns the number of times a specified value occurs in a tuple
Parameter
- value: Required. The item to search for

print("\n--------count()--------\n")
xlist = (1, 3, 7, 8, 7, 5, 4, 6, 8, 5)

num = xlist.count(5)

print(num)  # 2

index()

index(): finds the first occurrence of the specified value.
- The index() method raises an exception if the value is not found.
Parameter:
- value: Required. The item to search for

print("\n--------index()--------\n")
thistuple = (1, 3, 7, 8, 7, 5, 4, 6, 8, 5)

x = thistuple.index(8)

print(x)    # 3

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