"Python Notes" Lesson II (ii): List

Description

The list in Python is similar to an array in other high-level languages, but Python's list is much easier to manipulate.

The main focus of the list in Python is on the operation of the list parameters, focusing on the following:

Names.append (Names.count (Names.extend (Names.index (Names.insert (Names.pop (Names.remove) (Names.reverse (Names.sort (

The following is basically a description of the above operation.

1. Basic operation

• The basic operation is as follows:

Names[num]: The element sorted as number num NAMES[-1:]: Last 1 elements names[-5:]: Last 5 elements names[-5:-1]: last 5 elements, but excluding last 1 elements (i.e. excluding names[-1]) Names[:5] : Starting 5 elements (i.e. excluding names[5]) Names[0:5]: Starting 5 elements (i.e. excluding names[5]) names[10:15]:names[10] to names[14]

• The above has the scope of the case, the front and back two digits, can be recorded as: "Out of the box", that is, after not taken before

· Do a simple test in the following environment:

>>> names = [' Xpleaf ', ' Yonghaoyip ', ' CL ']>>> names.extend (range) >>> names[' xpleaf ', ' Yonghaoyip ', ' CL ', 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 2 8, 29]

(1) Names[num]: An element sorted as a number num

>>> names[2] ' CL '

(2) Names[-1:]: Last 1 elements

>>> names[-1:][29]

(3) Names[-5:]: last 5 elements

>>> names[-5:][25, 26, 27, 28, 29]

(4) Names[-5:-1]: The last 5 elements, but excluding the last 1 elements (i.e. excluding names[-1])

>>> names[-5:-1][25, 26, 27, 28]

(5) Names[:5] or Names[0:5]: start 5 elements (i.e. excluding names[5])

>>> names[:5][' xpleaf ', ' Yonghaoyip ', ' cl ', 0, 1]>>> names[0:5][' xpleaf ', ' Yonghaoyip ', ' cl ', 0, 1]

(6) names[10:15]:names[10] to names[14]

>>> Names[10:15][7, 8, 9, ten, 11]>>> names[10]7>>> names[14]11>>> names[15]12

2.append () parameter

• Basic features: Adding elements to the list

• Basic Syntax:

Names.append (' Xpleaf ')

The append () parameter adds an element to the last face of the list and can only add one at a time;

• The demo is as follows:

>>> names.append (' xpleaf ') >>> names[' xpleaf ', ' Yonghaoyip ', ' CL ', 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ------------------------------------

3.count () parameter

• Basic function: Count the number of identical elements in the list

• Basic Syntax:

Names.count (' Xpleaf ')

• The demo is as follows:

>>> names[' xpleaf ', ' Yonghaoyip ', ' CL ', 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, (+), (+), (+), (+), +,-2, ' Xpleaf ']>>> names.count (' xpleaf ')

4.extend () parameter

• Basic functionality: Merge elements from another list into the current list

• Basic Syntax:

Names.extend (range (10)) is equivalent to the following: Names = names + range (Ten) ===> list can also be added directly, the characteristics of the sequence in Python

• The demo is as follows:

>>> names[' xpleaf ',  ' Yonghaoyip ',  ' CL ',  0,  1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,  14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,  26, 27, 28, 29,  ' Xpleaf ']>>> range (Ten)     ===> The output of range () is already a list [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>>>  names.extend (range) >>> names[' xpleaf ',  ' Yonghaoyip ',  ' CL ',  0, 1,  2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,  27, 28, 29,  ' Xpleaf ',  0, 1, 2, 3, 4, 5, 6, 7,  8, 9] 

append () adds the elements in the list, if written as follows:

Names.append (range) ===> only adds a list element at the end of the names list [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

5.index () parameter

• Basic function: Find the index number of the list element you want to find

• Basic Syntax:

Names.index (' Xpleaf ')

• If there are multiple identical elements in the list, index () finds only the 1th number of the same element

• The demo is as follows:

>>> names.append (' cl ') >>> names[' xpleaf ', ' Yonghaoyip ', ' CL ', 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, All, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ' CL ']>>&, +, (+), (+), (+), (+), (+) Gt Names.index (' xpleaf ') 0>>> names.index (' cl ') 2>>> names[2] ' cl '

6.inset () parameter

• Basic function: Insert an element in a position in a list

• Basic Syntax:

Names.insert (6, ' love ') ===> inserts the element ' love ' in the position where the index number of the list is 6

• The demo is as follows:

>>> names[' xpleaf ',  ' Yonghaoyip ',  ' CL ',  0,  1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,  14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,  26, 27, 28, 29,  ' Xpleaf ',  0, 1, 2, 3, 4, 5, 6,  7, 8, 9,  ' CL ']>>> names.insert (6, ' love ') >>> names[' xpleaf ',   ' Yonghaoyip ',  ' CL ', 0, 1, 2,  ' love ',  3, 4, 5, 6, 7,  8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,  20, 21, 22, 23, 24, 25, 26, 27, 28, 29,  ' Xpleaf ',  0, 1, 2, 3, 4, 5, 6, 7, 8, 9,  ' CL ']>>>  Names[6] ' love ' 

--Small integrated operation: replace ' xpleaf ' in the above list with ' Xpleaf_yip '

• Clumsy methods that do not take full advantage of Python features:

>>> while True: ... if Names.count (' xpleaf ') = = 0: ... else: ... names[names.index (' xpleaf ')] = ' Xpleaf_yip ' ... >>> names[' Xpleaf_yip ', ' Yonghaoyip ', ' CL ', 0, 1, 2, ' Love ', 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 , (+), 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ' CL ', (+), (+), (+), (+), ' Xpleaf_yip ', +-

• Although the goal can be achieved, the method is actually rather stupid;

• Ways to take advantage of Python features:

>>> for I in range (Names.count (' Xpleaf ')): ... names[names.index (' xpleaf ')] = ' Xpleaf_yip ' ... >>> name s[' Xpleaf_yip ', ' Yonghaoyip ', ' CL ', 0, 1, 2, ' Love ', 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, , at, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ' CL ', and ' Xpleaf_yip ',.

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"Python Notes" Lesson II (ii): List