从Python中的字典列表中提取键值对

Question

I have dictionary in the following format stored inside a list.Below are listed the 12 members (dictionaries) of list switch_ports

[
{'type': 'port', 'number': 1, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:011', 'desc': 's1-eth1'},
{'type': 'port', 'number': 2, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:012', 'desc': 's1-eth2'},
{'type': 'port', 'number': 1, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:021', 'desc': 's2-eth1'},
{'type': 'port', 'number': 2, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:022', 'desc': 's2-eth2'},
{'type': 'port', 'number': 1, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:031', 'desc': 's3-eth1'},
{'type': 'port', 'number': 2, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:032', 'desc': 's3-eth2'},
{'type': 'port', 'number': 1, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:041', 'desc': 's4-eth1'},
{'type': 'port', 'number': 2, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:042', 'desc': 's4-eth2'},
{'type': 'port', 'number': 1, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:051', 'desc': 's5-eth1'},
{'type': 'port', 'number': 2, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:052', 'desc': 's5-eth2'},
{'type': 'port', 'number': 1, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:061', 'desc': 's6-eth1'},
{'type': 'port', 'number': 2, 'port_state': 1, 'state': 'active', 'port_id': '00:00:00:00:00:00:02:062', 'desc': 's6-eth2'}]

From the list switch_ports I want to access port_id above. How do I do that?

If I do

for port in switch_ports:
      print(port)

I get the same output as above. However If I try to access individual key-value pairs as below.

for port in switch_ports:
      print(port[port_id])

How do I get the port_id (eg 00:00:00:00:00:00:02:062 ) from the list switch_ports

Answer 1

You are almost there. Just use port_id as a string, like this

for port in switch_ports:
      print(port["port_id"])

If you want to gather all the port_id s as a list, then use list comprehension like this

port_ids = [port["port_id"] for port in switch_ports]

Online Demo

Answer 2

An alternative, use itemgetter from the operator module:

>>> import operator
>>> operator.itemgetter('port_id')
<operator.itemgetter object at 0x7f318d7b8b90>
>>> port_id = operator.itemgetter('port_id')
>>> for port in switch_ports:
...     print port_id(port)
... 

prints:

00:00:00:00:00:00:02:011
00:00:00:00:00:00:02:012
00:00:00:00:00:00:02:021
00:00:00:00:00:00:02:022
00:00:00:00:00:00:02:031
00:00:00:00:00:00:02:032
00:00:00:00:00:00:02:041
00:00:00:00:00:00:02:042
00:00:00:00:00:00:02:051
00:00:00:00:00:00:02:052
00:00:00:00:00:00:02:061
00:00:00:00:00:00:02:062