[python tutorial] Python tuple

Python tuples

Python tuples are similar to lists, except that the elements of the tuple cannot be modified.

Use parentheses for tuples and square brackets for lists.

Tuple creation is very simple, just add elements in brackets and separate them with commas.

The following example:

tup1 = ('physics', 'chemistry', 1997, 2000);
tup2 = (1, 2, 3, 4, 5 );
tup3 = "a", "b", "c", "d";

Create an empty tuple

tup1 = ();

When the tuple contains only one element, you need to add a comma after the element

tup1 = (50,);

element Groups are similar to strings. The subscript index starts from 0 and can be intercepted, combined, etc.

Accessing tuples

Tuples can use subscript indexes to access the values ​​in the tuple, as shown in the following example:

#!/usr/bin/python

tup1 = ('physics', 'chemistry', 1997, 2000);
tup2 = (1, 2, 3, 4, 5, 6, 7 );

print "tup1[0]: ", tup1[0]
print "tup2[1:5]: ", tup2[1:5]

The output result of the above example:

tup1[0]:  physics
tup2[1:5]:  [2, 3, 4, 5]

Modify the tuple

The element values ​​in the tuple are not allowed to be modified, but we can connect and combine the tuples, as shown in the following example:

#!/usr/bin/python

tup1 = (12, 34.56);
tup2 = ('abc', 'xyz');

# 以下修改元组元素操作是非法的。
# tup1[0] = 100;

# 创建一个新的元组
tup3 = tup1 + tup2;
print tup3;

The output result of the above example:

(12, 34.56, 'abc', 'xyz')

Delete a tuple

Element values ​​in a tuple are not allowed to be deleted, but we can use the del statement to delete the entire tuple, as shown in the following example:

#!/usr/bin/python

tup = ('physics', 'chemistry', 1997, 2000);

print tup;
del tup;
print "After deleting tup : "
print tup;

Above example After the tuple is deleted, the output variable will have exception information, and the output is as follows:

('physics', 'chemistry', 1997, 2000)
After deleting tup :
Traceback (most recent call last):
  File "test.py", line 9, in <module>
    print tup;
NameError: name &#39;tup&#39; is not defined

Tuple operator

Like strings, the + sign and * can be used between tuples number to perform operations. This means that they can be combined and copied, resulting in a new tuple.

Python expression

Result

Description

len((1, 2, 3) ) 3 Calculate the number of elements

(1, 2, 3) + (4, 5, 6) (1, 2, 3, 4, 5, 6) Connect

['Hi !'] * 4 ('Hi!', 'Hi!', 'Hi!', 'Hi!') Copy

3 in (1, 2, 3) True Whether the element exists

for x in (1, 2, 3): print x, 1 2 3 Iteration

Tuple index, interception

Because the tuple is also a sequence, we can access the tuple The element at the specified position in the index can also be intercepted, as shown below:

Tuple:

L = ('spam', 'Spam', 'SPAM!')

Python expression

Result

Description

L[2] 'SPAM!' Read the third element

L[-2] 'Spam' Reverse Read in the direction; read the penultimate element

L[1:] ['Spam', 'SPAM!'] Intercept element

No closing delimiter

Any unsigned object, separated by commas, defaults to a tuple, as shown in the following example:

#!/usr/bin/python

print 'abc', -4.24e93, 18+6.6j, 'xyz';
x, y = 1, 2;
print "Value of x , y : ", x,y;

The above example allows the result:

abc -4.24e+93 (18+6.6j) xyz
Value of x , y : 1 2

tuple built-in function

Python element The group contains the following built-in functions

serial number

method and description

1 cmp(tuple1, tuple2)
Compares two tuple elements.

2 len(tuple)
Calculate the number of tuple elements.

3 max(tuple)
Returns the maximum value of the element in the tuple.

4 min(tuple)
Returns the minimum value of the element in the tuple.

5 tuple(seq)
Convert the list to a tuple.

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