Python core Programming Read Pen 5: Mappings and collection types

Seventh chapter mapping and aggregation capabilities

A dictionary (the only mapping type in Python)

1 basic

Create and assign values:

Normal creation: >>>dict = {' name ': ' Earth ', ' Port ': 80}

Use the Factory function Dict () to create:

>>> fdict = Dict ([' X ', 1], [' Y ', 2])
>>> fdict
{' Y ': 2, ' X ': 1}
Use Fromkeys () to create a default dictionary:

>>> ddict = {}.fromkeys (' x ', ' Y '),-1)
>>> ddict
{' Y ':-1, ' X ':-1}

>>> edict = {}.fromkeys (' foo ', ' Bar ')
>>> Edict
{' Foo ': None, ' Bar ': none}
　　

To access the values in the dictionary:

dict[' name ']

　　　　

>>>> for key in Dict2. Keys():
... print ' key=%s, value=%s '% (key, Dict2[key])

>>>> for key in Dict2:
... print ' key=%s, value=%s '% (key, Dict2[key])

Has_key () and in, not to determine if a key is in the dictionary

　　

To delete a dictionary element and dictionary:

Del dict[' name ']

Dict.clear ()

Del Dict

Dict.pop (' name ') deletes and returns an entry with the key ' name '

　　　　　　

2 operator

Python core Programming Read Pen 5: Mappings and collection types