Summary of usage of python dictionary operations

Basic syntax:

dict = {'ob1':'computer', 'ob2':'mouse', 'ob3':'printer'}

Tips:

The dictionary contains lists: dict={'yangrong':['23','IT'],"xiaohei":['22','dota']}

The dictionary contains dictionaries: dict={'yangrong':{"age":"23","job":"IT"},"xiaohei":{"'age':'22','job': 'dota'"}}

Available commands:

root@yangrong:~# cd /python

root@yangrong:/python# python

Python 2.7.5+ (default, Sep 19 2013,13:48:49)

[GCC 4.8.1] on linux2

Type "help","copyright", "credits" or "license" for moreinformation.

>>> ; import tab

>>> d={}

>>> d.

d.class( d.ge( d.len ( d.setitem( d.has_key( d.setdefault(

d.cmp( d.lt( d.sizeof( d.items( d.items( d.update(

d .contains( d.getitem( d.ne( d.str( d.iteritems( d.values(

d.delattr( d.gt( d.new( ) d.subclasshook( d.iterkeys( d .viewitems(

d.delitem( d.hash d.reduce( d.clear( d.itervalues(

d.doc d.init( d.reduce_ex( d .copy (           

d.format(       d.le ( d.setattr( d.get( d.popitem( d.popitem() {}

>>> nameinfo['a1']='yangrong' #If there is a1 primary key in the dictionary, overwrite the original value, if not, add

> >> nameinfo

{'a1': 'yangrong'}

Traverse the dictionary primary key and key value

>>> for k, value innameinfo. items():

... print k,value

...

a1 yangrong

View all primary keys in the dictionary

>>> dict = {'ob1':'computer','ob2' :'mouse', 'ob3':'printer'}

>>>

>>>

>>> dict .keys()

['ob2', 'ob3', 'ob1']

Determine whether the primary key exists in the dictionary

>>> dict. keys()

['ob2', 'ob3', 'ob1']

>>> dict.has_key('ob2') #or'ob2' in dict

True

>>> dict.has_key('ob4')

False

Some people also use the loop method To judge

for key in dict.keys():

But this method is not concise enough after all,

View all key value contents of the dictionary

> ;>> dict = {'ob1':'computer','ob2':'mouse', 'ob3':'printer'}

>>> dict.values()

['mouse', 'printer', 'computer']

List all items

>>> dict.items()

[('ob2', 'mouse'), ('ob3', 'printer'),('ob1', 'computer')]

Clear the dictionary

>> > dict.clear()

>>> dict

{}

Copy dictionary

>>> dict

{'ob2': 'mouse', 'ob3': 'printer', 'ob1':'computer'}

>>> a=dict

>>> a

{'ob2': 'mouse', 'ob3': 'printer', 'ob1':'computer'}

>>> b=dict.copy()

>>> b

{'ob2': 'mouse', 'ob3': 'printer', 'ob1': 'computer'}

Compare dictionary

>>> cmp(a,b)

First compare the primary key length, then compare the key size, and then compare the key value size, (No. A large one returns 1, a small one returns -1, the same returns 0)

Update dictionary

>>>dict={'yangrong':{"age":"23" ,"job":"IT"},"xiaohei":{"'age':'22','job':'dota'"}}

>>> dict

{'xiaohei':set(["'age':'22','job':'dota'"]), 'yangrong': {'age': '23', 'job':'IT '}}

>>> dict['xiaohei']=111 #Modify the first-level dictionary

>>> dict

{'xiaohei ': 111, 'yangrong': {'age': '23','job': 'IT'}}

>>> dict['yangrong']['age']= 25 #Modify the secondary dictionary

>>> dict

{'xiaohei': 111, 'yangrong': {'age': 25,'job': 'IT' }}

>>> dict={'yangrong':['23','IT'],"xiaohei":['22','dota']}

>>>dict['xiaohei'][1]="dota2" #Modify an item in the list in the dictionary, 1 represents the second string in the list.

>>> dict

{'xiaohei': ['22', 'dota2'], 'yangrong':['23', 'IT']}

Delete dictionary elements

>>> dict

{'xiaohei': ['22', 'dota2'], 'yangrong':['23', 'IT']}

>>> del dict['xiaohei']           #Delete xiaohei key value

>>> dict

{' yangrong': ['23', 'IT']}

>>> dict

{'yangrong': ['23', 'IT']}

>>>

>>> del dict['yangrong'][1] #Delete every 2-character value of the yangrong primary key

>> > dict

{'yangrong': ['23']}

Delete the entire dictionary

>>> dict

{' yangrong': ['23']}

>>> dict.clear() #Same as del dict

>>> dict

{ }

Split the string into a list

>>> s="hello world bye"

>>> s.split() # Used to read regular text, modify it using a list, and then write it to the file.

['hello', 'world', 'bye']

Convert the list to a string

S.split(str, ' ') #WillstringConvertlist, split by spaces

Storage dictionary (pickle serialization)

#Need to import the pickle module import pickle

Save the dictionary content to the file

f=file('data.txt','wb') #Create a new file data.txt, 'wb', b is an open block file, for Device files are useful

pickle.dump(a,f) #Serialize a and store it in the file

f.close()

Read the content into the dictionary (deserialize ization)

a=open('data.txt','rb') #Open file

print pickle.load(a) #Deserialize all contents

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