Introduction to Python: 4000 words through Python data type tuples

Public account: You and the cabin by: Peter Editor: Peter

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Tuples tuple

In the Python data type introduced earlier: list list, we found that list can be modified. But there are times when you need to create a series of elements that cannot be modified, and another ordered data type in Python, a tuple, can do the job.

The overall layout of this article:

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In the future, I will write a special article to answer this question, mainly from four aspects:

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Tuples create

Tuples use parentheses in Python(a)Enclosed, the list is in square brackets[]The enclosed
Elements in tuples are separated by commas
The elements in a tuple can be any Python data type
A tuple is a sequence, like a list, but the elements in a tuple cannot be changed

Create an empty tuple

a = ()
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a
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The following result indicates that an empty tuple was created:

(a)Copy the code

type(a)
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tuple
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A single element

b = (3.)# numeric
b
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(3)Copy the code

type(b)  Tuple = tuple
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tuple
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c = ("python".)The # character type
c
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('python',)
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type(c)
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tuple
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d = (["python"."java".3],)  There is only one element, and it is a list
d
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(['python', 'java', 3],)
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type(d)
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tuple
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Note that when there is only one element in a tuple, it must be followed by a comma, otherwise Python will not consider it a tuple:

e = (3)  # no comma, system default is numeric
e
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3
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type(e)  
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int
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f = (["python"."java"])  There is only one element list
f
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['python', 'java']
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type(f)   The system defaults to list
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list
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As the above examples show, if you create a tuple with only one element (of any Python type), you must enclose parentheses at the end

Multiple elements

Elements can be of different data types through tuples of multiple elements

t1 = (1.2.3)   # all numeric types
t1
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(1, 2, 3)
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type(t1)
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tuple
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t2 = (1."pyton"."java")  # numeric + string
t2
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(1, 'pyton', 'java')
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type(t2)
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tuple
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t3 = (1[1.2.3]."python")    # numeric + list + string
t3
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(1, [1, 2, 3], 'python')
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type(t3)
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tuple
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Consider this amazing example: when we assign the variable T4, there are three values following it;

As you can see from the results, Python treats them as a whole and puts them into a tuple

t4 = 100."python"."hello"
t4
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(100, 'python', 'hello')
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type(t4)  The data type is a tuple
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tuple
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Elements in a tuple can also be of tuple type

t5 = (1.2, (3.4.5),"python")  The (3,4,5) parts are tuples
t5
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(1, 2, (3, 4, 5), 'python')
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type(t5)
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tuple
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Created by the tuple function

When creating with a tuple, enclose the elements in parentheses

tuple1 = tuple((1.3.5.7))  # Two layers of parentheses
tuple1
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(1, 3, 5, 7)
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type(tuple1)
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tuple
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If only one layer is used, an error is reported; The tuple method takes only one argument:

tuple(1.3.5.7)    
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---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-26-b16145832f5a> in <module>
----> 1 tuple(1,3,5,7)


TypeError: tuple expected at most 1 arguments, got 4
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tuple2 = tuple((1."c".5."python"))
tuple2
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tuple3 = tuple(((1.2.3].3."python".7))
tuple3
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Zip function creation

Zip is a higher-order function in Python, and its use will be explained later. We can also use it to create tuples

name = ["Xiao Ming"."Little red"."Chou"]
age = [20.28.19]

zip(name,age)  Generate a zip object
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<zip at 0x107d34320>
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list(zip(name,age)) The object is transformed into a list, in which the elements are tuples
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[(' Xiao Ming ', 20), (' Xiao Hong ', 28), (' Xiao Zhou ', 19)]Copy the code

tuple(zip(name,age))   # 2, convert to nested tuples in tuples
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(' Xiao Ming ', 20), (' Xiao Hong ', 28), (' Xiao Zhou ', 19)Copy the code

dict(zip(name,age))  It can also be converted to a dictionary (which is also a Python data type).
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{' Xiao Ming ': 20, 'Xiao Hong ': 28,' Xiao Zhou ': 19}Copy the code

Basic tuple operations

For the length of the

t6 = (0.1.2.3.4.5.6.7.8)   # Purely numerical
t6
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(0, 1, 2, 3, 4, 5, 6, 7, 8)
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t7 = ("python"."java"."c")   # character type
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type(t7)
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tuple
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len(t6)
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9
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len(t7)
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3
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Repeat tuple elements

t7 * 3  Duplicate 3 times
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('python', 'java', 'c', 'python', 'java', 'c', 'python', 'java', 'c')
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Add multiple tuples

t6 + t7
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(0, 1, 2, 3, 4, 5, 6, 7, 8, 'python', 'java', 'c')
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Look at the most value

Size is determined by the ASCII code of the elements in a tuple

max(t6)
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8
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min(t7)
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'c'
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t5
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(1, 2, (3, 4, 5), 'python')
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When Max or min is used, the data types of the elements in the tuple must be the same. Otherwise, an error will be reported:

max(t5)
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---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-41-f6f6f0f7436f> in <module>
----> 1 max(t5)


TypeError: '>' not supported between instances of 'tuple' and 'int'
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Member judgment in

1 in t6
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True
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10 in t6
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False
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Traverse the tuples

for i in t6:  Print through the elements of a tuple
    print(i)
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0, 1, 2, 3, 4, 5, 6, 7, 8Copy the code

Modify a tuple?

Do not modify

As we mentioned at the beginning, elements in tuples cannot be modified directly

t7
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('python', 'java', 'c')
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t7[1]
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'java'
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We get an error when we try to change Java to JavaScript because tuples themselves cannot be modified:

t7[1] = "JavaScript"     
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---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-47-7885d09b5b02> in <module>
----> 1 t7[1] = "JavaScript"


TypeError: 'tuple' object does not support item assignment
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Change it to a list

Because lists can be modified, we can first turn tuples into lists, then modify the elements in the corresponding lists, and then go back

t7
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('python', 'java', 'c')
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t7_1 = list(t7)  # 1. Turn to a list
t7_1
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['python', 'java', 'c']
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t7_1[1] = "javascript" # 2. Modify elements
t7_1
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['python', 'javascript', 'c']
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t7_2 = tuple(t7_1)  # 3, and then into tuples
t7_2
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('python', 'javascript', 'c')
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Index and slice

Tuples, like lists, are ordered data types in Python, and there are concepts of use and slicing

Using the index

Use index numbers to access tuple elements

t6.index(0)  # the index of element 0
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0
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t6.index(6)  # index number of element 6
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6
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t6[8]  # positive index
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8
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t6[-4]  Negative index number
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5
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t7.index("java")   Check the usage number of the element
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1
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t7[1]   View elements by index number
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'java'
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Using slice

The rules for using slices in tuples are exactly the same as for lists, and you can refer to the list article to learn.

The following is just a case study of using slicing in tuples:

t6[:7]
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(0, 1, 2, 3, 4, 5, 6)
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t6[1:8:2]
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(1, 3, 5, 7)
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t6[:8:2]   # Start at the beginning with step 2
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(0, 2, 4, 6)
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From the last element (index -1) to index -8 (not included), the step is -2

t6[-1: -8: -2]   
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(8, 6, 4, 2)
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t6[-2: -7: -2]
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(7, 5, 3)
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t6[1:8:3]
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(1, 4, 7)
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Tuples and list comparisons

The same

Are ordered data types in Python
Many of the same operations exist: length, maximum, membership, indexing, slicing, and so on

The difference between

Lists can be modified directly, not tuples; We can turn tuples into lists and then modify the elements indirectly
Tuples are faster than lists. If we define a variable and need to iterate over it constantly, using tuples is faster