python-Basics-string-list-Ganso-Dictionary 2

Pick Up: http://www.cnblogs.com/liu-wang/p/8973273.html

3 tuples

4 Introduction of the Dictionary 4.1 dictionary

<2> Dictionaries in software development

Variable info is a dictionary type:

    info = {‘name‘:‘班长‘, ‘id‘:100, ‘sex‘:‘f‘, ‘address‘:‘地球亚洲中国北京‘}

Description

• Dictionaries and lists are also capable of storing multiple data
• When an element is found in the list, it is based on the subscript
• When looking for an element in a dictionary, it is based on the ' name ' (that is, the colon: the preceding value, such as ' name ', ' id ', ' sex ') in the code above
• Each element of the dictionary consists of 2 parts, the key: value. For example ' name ': ' Monitor ', ' name ' is the key, ' monitor ' is the value

<3> Access Values by key

info = {' name ': ' Monitor ', ' ID ': +, ' sex ': ' f ', ' address ': ' Earth Asia China Beijing '}    print (info[' name '])    print (info[' Address ']) 

Results:

    班长    地球亚洲中国北京

If you access a nonexistent key, you will get an error:

>>> info[' age ']traceback (most recent call last):  File "<stdin>", line 1, in <module>  Keyerror: ' Age ' 

When we are unsure whether a key exists in the dictionary and want to get its value, you can use the Get method and set the default value:

>>> age = Info.get ("Age") >>> Age # ' age ' key does not exist, so age is none>>> type (age) <type ' Nonetype ' >>>> age = info.get (' 18 ') # returns the default value if it does not exist in info 18>>> age18  

4.2 Common operations for dictionaries 1

4.3 Common operations for Dictionaries 2

5 traversal

6 Public methods

Python built-in functions

Python contains the following built-in functions

Serial Number	Method	Description
1	CMP (ITEM1, ITEM2)	Comparison of two values
2	Len (item)	Count the number of elements in a container
3	Max (item)	Returns the maximum value of an element in a container
4	MIN (item)	Returns the element minimum value in the container
5	Del (item)	Delete a variable

Cmp

>>> CMP ("Hello","Itcast")-1>>> CMP ("Itcast","Hello")1>>> CMP ("Itcast","Itcast") 0>>> CMP ([1, 2], [3, 4])-1>>> CMP ([1, 2], [1, 1])1>>> CMP ([1, 2], [1, 2, 3])-1>>> CMP ({"a": 1}, {"b": 1})-1>>> CMP ({"a": 2}, {"a": 1})1>>> CMP ({"a": 2}, {"a": 2,"b": 1})-1

Note: When CMP compares the dictionary data, it compares the keys before comparing the values.

Len

>>> Len ("hello itcast")12>>> len ([1, 2, 3, 4])4> >> Len ((3,4))2>>> len ({"a""b" : 2})2

Note: When Len is manipulating the dictionary data, it returns the number of key-value pairs.

Max

>>> Max ("Hello Itcast")'T'>>> Max ([1,4,522,3,4])522>>> Max ({"a": 1,"b": 2})'b'>>> Max ({"a": 10,"b": 2})'b'>>> Max ({"C": 10,"b": 2})'C'

Del

Del has two uses, one of which is del plus a space and the other is Del ()

>>> A = 1>>>a1>>>dela>>>Atraceback (most recent): File"<stdin>", Line 1,inch<module>Nameerror:name'a'  is  notdefined>>> a = ['a','b']>>>delA[0]>>>a['b']>>>del(a)>>>Atraceback (most recent): File"<stdin>", Line 1,inch<module>Nameerror:name'a'  is  notDefined

Multidimensional List/Ganso access

>>> tuple1 = [(2,3), (4,5)]>>> tuple1[0] (2,3)>>> tuple1[1]:0]2>>> tuple1[1]:2]traceback (most recent): File"<stdin>", line1,In <module>indexerror:tuple index out of range>>> tuple1[1]:1]3>>> tuple1[2][2]traceback (most recent): File"<stdin>", line1,in <module>indexerror:list index out of Range>> > tuple2 = tuple1+[(3)]>>> tuple2[(2, 3), (4, 5), 3]>>> tuple2[2]3>>> tuple2[2][ 0] Traceback (most recent): File 1, Span class= "Hljs-keyword" >in <module>typeerror:  ' int ' object is not subscriptable       

7 References

python-Basics-string-list-Ganso-Dictionary 2