Python learning notes: usage examples of dictionaries

Functions used in the classic dictionary
Dict: Create a dictionary through a sequence pair such as other ing (such as other dictionaries) or (Key, value. Of course, dict is not very definite as a function. It is essentially a type. Like list.

Copy codeThe Code is as follows:
Items = [('name', 'zhang '), ('age', 42)]
D = dict (items)
D ['name']

Len (d): number of returned items
D [k]: The value above the return key k.
D [k] = v: set the value of k to k.
Del d [k]: delete this item in the dictionary.
K in d: Check whether d contains k keys. Note: You can only search for keys, but not for values.
Example of a simple phone book:

Copy codeThe Code is as follows:
# A simple database
# A dictionary with person names as keys. Each person is represented
# Another dictionary with the keys 'phone' and 'addr' referring to their phone
# Number and address, respectively.
People = {
'Alice ':{
'Phone': '123 ',
'Addr ': 'foo drive 23'
},
'Beth ':{
'Phone': '123 ',
'Addr ': 'bar street 42'
},
'Cecil ':{
'Phone': '123 ',
'Addr ': 'baz avenue 90'
}
}
# Descriptive labels for the phone number and address. These will be used
# When printing the output.
Labels = {
'Phone': 'phone number ',
'Add': 'address'
}
Name = raw_input ('name :')
# Are we looking for a phone number or an address?
Request = raw_input ('phone number (p) or address ()? ')
# Use the correct key:
If request = 'P': key = 'phone'
If request = 'A': key = 'addr'
# Only try to print information if the name is a valid key in
# Our dictionary:
If name in people: print "% s's % s is % s." % \
(Name, labels [key], people [name] [key])

Dictionary Method
Clear: clear all items in the dictionary.

Copy codeThe Code is as follows:
X. clear ()

Copy: A copy dictionary.

Copy codeThe Code is as follows:
Y = x. copy ()

Deepcopy: copy.

Copy codeThe Code is as follows:
From copy import deepcopy
D = {}
D ['names'] = ['as', 'sa']
C = d. copy ()
Dc = deepcopy (d)
D ['names']. append ('ad ')

Fromkeys: Creates a new dictionary for the specified key. The default value of each key is none.
Copy codeThe Code is as follows:
{}. Fromkeys (['name', 'age'])

Get: a more relaxed Method for accessing dictionary items.
Copy codeThe Code is as follows:
D. get ('name ')

Copy codeThe Code is as follows:
# A simple database using get ()
# Insert database (people) from Listing 4-1 here.
Labels = {
'Phone': 'phone number ',
'Add': 'address'
}
Name = raw_input ('name :')
# Are we looking for a phone number or an address?
Request = raw_input ('phone number (p) or address ()? ')
# Use the correct key:
Key = request # In case the request is neither 'P' nor 'A'
If request = 'P': key = 'phone'
If request = 'A': key = 'addr'
# Use get to provide default values:
Person = people. get (name ,{})
Label = labels. get (key, key)
Result = person. get (key, 'not available ')
Print "% s's % s is % s." % (name, label, result)

Has_key: Check whether the dictionary contains the given key. D. haos_key (). Returns True or False.

Items: returns the list of all dictionary items.

Iteritems: The methods are roughly the same, but an iterator instead of a list is returned.

Keys: returns the keys in the dictionary as a list. (Note the differences between the differentiation and items)

Iterkeys: return the iterator for the key.

Pop: obtain the value of the corresponding key, and then delete the key-value pair.

Popitem: a random item is displayed,

Setdefault: You can get the value related to the given key, and set the corresponding key value without the key in the dictionary.

Update: update a dictionary.

Copy codeThe Code is as follows:
D = {'1': 'D', '2': 's', '3': 'A '}
X = {'1', 'jk '}
D. update (x)

Values: returns the value in the dictionary in the form of a list.

Itervalues: the return value iterator.