The second lesson of the basic Python tutorial 0120

Learning lists and tuples today

1. Sequence

>>> a=[' RP ', 22]
>>> b=[' RY ', 55]
>>> Database=[a,b]
>>> Database
[' RP ', [' RY ', 55]]
>>>

2. Index

>>> hello= ' Nihao '
>>> Hello[0]
N
>>> #也可以这样写
>>> ' Nihao ' [0]
N
>>>

3. sharding

>>> numbers=[1,2,3,4,5,6,7,8,9,10]//number of use, positive count is starting from 0 counting, counting is also starting from 0. So the general last element is not good to take.
>>> Numbers[3:6]
[4, 5, 6]
>>> #分片
>>> Numbers[0:1]
[1]
>>> Numbers[7:10]
[8, 9, 10]
>>> Numbers[-1:-3]
[]
>>> Numbers[-3:-1]
[8, 9]
>>> numbers[-3:]//output until the last element
[8, 9, 10]
>>> Numbers[:3]//output from the first element to the specified element
[1, 2, 3]
>>> numbers[:]//Output all elements
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

A simple example:

>>> url=raw_input (' Please enter the URL: ')
Please enter the url:http://www.python.org
>>> Domain=url[11:-4]
>>> print "Domain name:" +domain
Domain Name:python
>>>

3.1 Shards--In larger steps

The above example increases the step size by 1, and the following can be used in different steps.

>>> Numbers[0:10:1]
[1, 2, 3, 4, 5, 6, 7, 8, 9, ten]//A:B:C where A is the specified starting bit, B is the specified bottom, and C is the specified The step size.
>>> Numbers[0:10:3]
[1, 4, 7, 10]
>>> Numbers[3:6:3]
[4]
>>>

A little Tip

>>> Numbers[::4]//need to extract the first of every 4, just set the step to 4.
[1, 5, 9]

The step can be negative, not 0; (negative is inverted output)
>>> Numbers[8:3:-2]
[9, 7, 5]
>>>

Simple summary: If you want to get the output you need to know how to set the ABC parameter.

4. Sequence addition

>>> #序列相加
>>> [1,2,3,4]+[5,6,7]
[1, 2, 3, 4, 5, 6, 7]
>>> [1,2,3]+ ' World '//list and string cannot be joined together

Traceback (most recent):
File "<pyshell#35>", line 1, in <module>
[1,2,3]+ ' World '
Typeerror:can only concatenate list (not "str") to List
>>>

5. Multiplication

>>> ' Nihao '//String multiplication
' Nihao Nihao nihao nihao Nihao '
>>> [1,5]*3//List multiplication
[1, 5, 1, 5, 1, 5]
>>> x= ' Hello '//String multiplication
>>> x*5
' Hellohellohellohellohello '
>>> wo=[you]*6

Traceback (most recent):
File "<pyshell#42>", line 1, in <module>
Wo=[you]*6
Nameerror:name ' You ' are not defined
>>> wo =[none]*2//Here you can see that only the Pyhton definition of the keyword can not add ', but not the keyword will need to add ' ' to the character of the shape In-band operation.
>>> wo
[None, none]
>>>

7. Membership--in
>>> u=[' foo ', ' wo ', ' koo ']//list not allowed to find non-strings
>>> ' O ' in U
False
>>> ' foo ' in U
True
>>> sub= ' ni$ $wo%%ta '
>>> ' $ ' in sub
True
>>> ' P ' in ' Python '
True
>>>

8. Length minimum and maximum value

>>> members=[100,34,68]
>>> Len (members)
3
>>> min (members)
34
>>> Max (members)
100
>>> Len ([45,26])
2
>>> min ([45,26])
26
>>> len (' Jack ')
4
>>> min (' abcxyz ')
A
>>> Max (2+3,5+6)
11
>>>

9. List

9.1 List

>>> #list functions
>>> list (' hello ')//Use list to convert a string into a list
[' H ', ' e ', ' l ', ' l ', ' O ']
>>> x=[1,21,1]
>>> x[1]=2
>>> x
[1, 2, 1]
>>> name=[' Alice ', ' Bob ', ' Tom '
>>> del name[2]//delete elements from a list
>>> Name
[' Alice ', ' Bob ']
>>>

9.2 Shard Assignment

>>> name=list (' Perl ')
>>> Name
[' P ', ' e ', ' r ', ' L ']
>>> name[2:]
[' R ', ' L ']
>>> ' arr ' =name[2:]//string cannot be directly assigned if not list
Syntaxerror:can ' t assign to literal
>>> name[2:]=list (' arr ') can be assigned after//list
>>> Name
[' P ', ' e ', ' a ', ' R ', ' R ']

Note: The assignment of lists and lists

>>> number=[1,5]
>>> number[2:]=[2,3,4]
>>> number
[1, 5, 2, 3, 4]
>>> number=[1,2,3,4,5,6,7,8,9,10]
>>> number[2:9:2 ]=[11,12,13,14 "              //To specify a step assignment
>>> number
[1, 2, one, 4, ten, 6,, 8, all, ten]
>>> number[2:9:2]= [11,12,13,14,15 ]

Adding a 15 to the range of the original list can cause errors.
Traceback (most recent):
File "<pyshell#12>", line 1, in <module>
NUMBER[2:9:2]=[11,12,13,14,15]
Valueerror:attempt to assign sequence of size 5 to extended slice of size 4
>>>

9.3 List Methods

Append

>>> #列表方法--append Call Method: Object. Method (Parameter)
>>> lst=[1,2,3]
>>> Lst.append (4)
>>> LST
[1, 2, 3, 4]
>>> #append用于在列表末尾添加新的对象
>>>

Count

>>> #count用于统计某个元素在列表中的出现次数
>>> [' to ', ' being ', ' or ', ' not ', ' to ', ' being ', ' is ', ' a ', ' Question '].count (' to ')
2
>>> x=[1,2,[3,4],5,[3,4],[3,[7,8]]
>>> X.count (3)
0
>>> X.count ([3,4])
2
>>> X.count ([7,8])
0
>>>

Extend

>>> #extend用于在列表的末尾一次性追加另一个序列中的多个值 (You can expand your existing list with a new list)
>>> a=[1,2,3]
>>> b=[10,11,12]
>>> A.extend (b)
>>> A
[1, 2, 3, 10, 11, 12]
>>> #此操作看起来像连接, the difference is: The Extend method modifies the extended sequence, and the original connection returns a completely new list
>>> a=[1,2,3]
>>> b=[4,5,6]
>>> a+b
[1, 2, 3, 4, 5, 6]
>>> A
[1, 2, 3]
>>>

Insert

>>> #insert用于将对象插入到列表中
>>> numbers=[1,2,3,4,5,6,7,8]
>>> Numbers.insert (3, ' four ')
>>> numbers
[1, 2, 3, ' Four ', 4, 5, 6, 7, 8]
>>> numbers[1:7:2]=[' R ']//There is a problem here, I specify that the start is 1, the end point is 7, every two steps will be ' R ' inserted, but doing so will cause the end of the new element with the insertion of the change,

Traceback (most recent calls last):// to not complete this requirement.
File "<pyshell#46>", line 1, in <module>
numbers[1:7:2]=[' R ']
Valueerror:attempt to assign sequence of size 1 to extended slice of size 3
>>>

Index

>>> #index用于从列表中找出某个值第一个匹配项的索引位置
>>> a=[' wo ', ' he ', ' ni ', ' hai ', ' You ', ' ta ']
>>> a.index (' wo ')
0
>>> a.index (' ji ')//Call index function not found, return error

Traceback (most recent):
File "<pyshell#52>", line 1, in <module>
A.index (' Ji ')
ValueError: ' Ji ' isn't in list
>>>

Pop

>>> #pop移除列表中的一个元素 (the last one by default)
>>> x=[1,2,3]
>>> X.pop ()
3
>>> x
[1, 2]
>>> X.pop (0)
1
>>> x
[2]
>>> x=[1,2,3,4,5,6,7,8,9]
>>> X.pop ([1:8:2])
Syntaxerror:invalid syntax

Remove

>>> #remove The first occurrence of a value in the list to be removed
>>> a=[' to ', ' being ', ' or ', ' not ', ' to ', ' being ', ' is ', ' a ', ' question ']
>>> a.remove (' be ')
>>> A
[' to ', ' or ', ' no ', ' to ', ' being ', ' is ', ' a ', ' question ']

Sort

>>> #sort用于在原位置对列表进行排序, sorting in the original position means changing the original list so that the elements can be arranged in a certain order, rather than simply returning a copy of the sorted list
>>> x=[1,2,3]
>>> X.sort ()
>>> x
[1, 2, 3]
>>> x=[5,9,4]
>>> X.sort ()
>>> x
[4, 5, 9]
>>> Sort (5,9,8)

Sorted//Is a function, called directly, without. Calling

>>> x=[7,8,2,9,4,0,9,8,6]
>>> y=x[:]
>>> y
[7, 8, 2, 9, 4, 0, 9, 8, 6]
>>> Y.sort ()
>>> y
[0, 2, 4, 6, 7, 8, 8, 9, 9]
>>> y=sorted (x)
>>> y
[0, 2, 4, 6, 7, 8, 8, 9, 9]
>>> sorted (' python ')
[' H ', ' n ', ' o ', ' P ', ' t ', ' Y ']
>>> sorted (' x ', ' BD ', ' C ')

Traceback (most recent):
File "<pyshell#98>", line 1, in <module>
Sorted (' x ', ' BD ', ' C ')
TypeError: ' str ' object is not callable
>>> Sorted (' d ', ' a ', ' C ')

Traceback (most recent):
File "<pyshell#99>", line 1, in <module>
Sorted (' d ', ' a ', ' C ')
TypeError: ' str ' object is not callable
>>>

Reverse//Just the opposite of sort

>>> #reverse将列表中的元素反向存放
>>> x=[3,2,1]
>>> X.reverse ()
>>> x
[1, 2, 3]
>>>

10. Advanced Sorting

CMP, which can be analogous to the strcmp function in a C-language string function

>>> CMP (42,39)
1
>>> CMP (' A ', ' Z ')
-1
>>> cmp (' iOS ', ' UMP ')
-1
>>> numbers=[8,2,9,7]
>>> Numbers.sort (CMP)
>>> numbers
[2, 7, 8, 9]
>>>

11. Tuples: Immutable sequences

>>>
(1, 2, 3)
>>> (a)
(1, 2, 3)
>>> (42.)
42.0
>>> (42,)
(42,)
>>> 6+ (40.)
46.0
>>> (42/8)
15
>>> (42)
126
>>> (40+2.)
126.0
>>> (40+2,)
(42, 42, 42)
>>>

Tuple

This function is to turn a sequence into a tuple

>>> tuple ([+])
(1, 2, 3)
>>> tuple (' abc ')
(' A ', ' B ', ' C ')
>>> tuple ((' Uji '))
(' U ', ' j ', ' I ')
>>>

The second lesson of the basic Python tutorial 0120