Python Learning notes: an example of using a dictionary

Classic Dictionary Use functions
Dict: A dictionary is created by a sequence of other mappings (such as other dictionaries) or (keys, values). Of course dict becomes a function is not very exact, it is essentially a type. Like a list.

The code is as follows:

items=[(' name ', ' Zhang '), (' Age ', 42)]
D=dict (items)
d[' name ']

Len (d): Returns the number of items
D[K]: Returns the value above the key K.
D[K]=V: Sets the value of K to K.
Del D[k]: Delete this item in the dictionary.
K in D: Check if D contains an entry with a key of K. Note: You can only look up keys and not look up values.
Simple Phone This example:

The code is as follows:

# A Simple Database
# A dictionary with the person names as keys. Each person is represented as
# Another dictionary with the Keys ' phone ' and ' addr ' referring to their phone
# number and address, respectively.
People = {
' Alice ': {
' Phone ': ' 2341 ',
' Addr ': ' Foo drive 23 '
},
' Beth ': {
' Phone ': ' 9102 ',
' Addr ': ' Bar Street 42 '
},
' Cecil ': {
' Phone ': ' 3158 ',
' Addr ': ' Baz Avenue 90 '
}
}
# Descriptive labels for the phone number and address. These'll be used
# when printing the output.
Labels = {
' Phone ': ' Phone number ',
' Addr ': ' Address '
}
Name = Raw_input (' Name: ')
# is we looking for a phone number or an address?
Request = Raw_input (' Phone number (p) or address (a)? ')
# Use the correct key:
If request = = ' P ': key = ' phone '
If request = = ' A ': key = ' addr '
# only try to print information if the name was a valid key in
# Our Dictionary:
If name in People:print "%s ' s%s" is%s. "% \
(name, Labels[key], People[name][key])

Dictionary methods
Clear: Clears all items in the dictionary.

The code is as follows:

X.clear ()

Copy: Shallow copy dictionary.

The code is as follows:

Y=x.copy ()

Deepcopy: Also copy, to see the difference from copy.

The 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, and the default corresponding value for each key is none.

The code is as follows:

{}.fromkeys ([' Name ', ' age '])

Get: A more relaxed way to access dictionary entries.

The code is as follows:

D.get (' name ')

The code is as follows:

# A Simple database using Get ()
# Insert Database (people) from Listing 4-1.
Labels = {
' Phone ': ' Phone number ',
' Addr ': ' Address '
}
Name = Raw_input (' Name: ')
# is we looking for a phone number or an address?
Request = Raw_input (' Phone number (p) or address (a)? ')
# 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 is%s. '% (name, label, result)

Has_key: Checks whether the dictionary contains the given key. D.haos_key (). The value returns True, False.

Items: Returns all dictionary items as a list.

Iteritems: The method is approximately the same, but returns an iterator instead of a list.

Keys: Returns the keys in the dictionary as a list. (Note the distinction between items)

Iterkeys: Returns an iterator for the key.

Pop: Gets the value corresponding to the given key, and then deletes the key-value pair.

Popitem: pops up a random item,

SetDefault: You can get the value associated with a given key, and you can set the corresponding key value without the key in the dictionary.

Update: Updates another dictionary with one dictionary.

The code is as follows:

d={' 1 ': ' d ', ' 2 ': ' s ', ' 3 ': ' A '}
x={' 1 ', ' JK '}
D.update (x)

Values: Returns the value in the dictionary as a list.

Itervalues: Returns a worthwhile iterator.

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