Python Learning (11) Python Data type: Dictionary (important)

Dictionary dict:

A dictionary is actually the equivalent of a map in Java to store key-value pairs. The data stored in it is unordered.

If there is such a data:

t1=[' name ', ' age ', ' sex '

t2=[' Tom ', ' Male '

by Zip (t1,t2) you can get to such data [(' Name ', ' Tom '), (' Age ', ' + '), (' Sex ', ' male ')]

The dictionary definition is done through {}.

A dictionary is the only type of mapping (hash table) in Python, where the Field object is variable, but the key of the Dictionary object must be immutable, and a dictionary can contain key values of the type.

Use keys () or values () to return the dictionary's key list or value list.

Items () returns a tuple of key-value pairs.

Dictionary Creation Method:

1. {}

For example d={' name ': ' Tom ', ' age ': +, ' sex ': ' Male '}

2, Factory method Dict ()

D = dict ()
D = dict (name= "Nico", age=23)
D = dict ([' Name ', "Nico"], [' Age ', 23])

3, built-in Method Fromkeys (), this comparison is suitable for the dictionary keys have the same value.

Ddict={}.fromkeys ((' x ', ' Y '),-1)

get {' x ':-1, ' Y ':-1}

Iterate through a dictionary

1d={'name':'Tom',' Age': 29,'Sex':'male'}2 3  forKinchD:4     Printk5 6 It's the same as this print. 7 8  forKinchD.keys ():9     PrintK

　　　　　　　　　　　　　　　　　　　　

How to do the dictionary:

1. New

d[' Tel ']= ' 1234568 '

At this point D is {' name ': ' Tom ', ' age ': ' Sex ': ' Male ', ' tel ': ' 12345678 '}

2. Modification

d[' Tel ']= ' 88888 '

3. Delete

Del (d[' tel ') Delete one of the key values in the dictionary

Del d Delete the entire dictionary

D.pop (' tel ') removes and returns an element with a key value of Tel

D.clear () empties the data in the entire dictionary

4. Take value

d[' name ']

Output Tom

If you take a nonexistent key value and report a Keyerroe exception, Python provides the D.get () method

such as D.get (' address ') is not output, you can also specify the default return value when not: D.get (' Address ', ' ERROR ') output error

Dictionary-related functions:

Type () CMP () str ()

　　

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Python Learning (11) Python Data type: Dictionary (important)