Python tuple

Python’s tuples are similar to lists, except that the elements of a 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 examples:

tup1 = ('physics', 'chemistry', 1997, 2000);

tup2 = (1, 2, 3, 4, 5);

tup3 = "a" , "b", "c", "d";

Create an empty tuple

tup1 = ();

Required when the tuple contains only one element Add a comma after the element

tup1 = (50,);

Tuples 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 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');

# The following operations to modify tuple elements are illegal.

# tup1[0] = 100;

# Create a new tuple

tup3 = tup1 + tup2;

print tup3;

The above example output result:

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

Delete the tuple

The element value in the tuple is not allowed to be deleted, but we can use the del statement to delete the entire tuple, as follows Example:

#!/usr/bin/python

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

print tup;

del tup;

print "After deleting tup : "

print tup;

After the above instance 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

print tup;

NameError: name 'tup' is not defined

Tuple operator

Like strings, tuples can be operated using + and * signs. 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) Connection

['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, intercept

Because the tuple is also a sequence, we can access The element at the specified position in the tuple can also intercept a section of elements in the index, as shown below:

Tuple:

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

OnPython expression

Description

L [2] 'spm!' Get the penultimate element

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

No closing delimiter

Any unsigned object separated by commas, default is a tuple, as follows 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 functions

Python tuples include 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.