python - Why what's wrong with this dict conversion of a lambda expression result object? -

was feeling smug thinking had best lambda expression in universe cooked return relevant network information ever needed using python , netifaces

>>> list(map(lambda interface: (interface, dict(filter(lambda ifaddress: ifaddress in (netifaces.af_inet, netifaces.af_link), netifaces.ifaddresses(interface) )))  , netifaces.interfaces())) 

but got this

traceback (most recent call last):   file "<stdin>", line 1, in <module>   file "<stdin>", line 1, in <lambda> typeerror: cannot convert dictionary update sequence element #0 sequence 

scaling bit

>>>dict(filter(lambda ifaddress: ifaddress in (netifaces.af_inet, netifaces.af_link), netifaces.ifaddresses("eth0"))) 

is problem is:

traceback (most recent call last):   file "<stdin>", line 1, in <module> typeerror: cannot convert dictionary update sequence element #0  sequence 

but can convert filter object list

 >>> list(filter(lambda ifaddress: ifaddress in (netifaces.af_inet, netifaces.af_link), netifaces.ifaddresses("eth0")))  [17, 2] 

but, that's not want. want is:

>>> netifaces.ifaddresses("tun2") {2: [{'addr': '64.73.0.0', 'netmask': '255.255.255.255', 'peer': '192.168.15.4'}]} >>> type (netifaces.ifaddresses("eth0")) <class 'dict'> 

so what's mucking cast back dictionary?

when given dictionary input, filter iterate , return keys dictionary.

>>> filter(lambda x: x > 1, {1:2, 3:4, 5:6}) [3, 5] 

thus feeding sequence of filtered keys new dict, not key-value-pairs. fix this: note call items() , how inner lambda getting tuple input.

list(map(lambda interface: (interface, dict(filter(lambda tuple: tuple[0] in (netifaces.af_inet, netifaces.af_link),                                                     netifaces.ifaddresses(interface).items()))),           netifaces.interfaces())) 

now that's not pretty... suggest changing code nested list- , dictionary-comprehension:

[(interface, {ifaddress: value            (ifaddress, value) in netifaces.ifaddresses(interface).items()           if ifaddress in (netifaces.af_inet, netifaces.af_link)})  interface in netifaces.interfaces()]