Python Pandas - Join left on multiple columns, add blanks to final data frame

Question

Im trying to do a multiple join, with the following:

host_data = temp_merged_data.merge(desc_data, left_on=['device_id, port'], how='left')

However am receiving the error:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python3.6/site-packages/pandas/core/frame.py", line 6389, in merge
    copy=copy, indicator=indicator, validate=validate)
  File "/usr/local/lib/python3.6/site-packages/pandas/core/reshape/merge.py", line 61, in merge
    validate=validate)
  File "/usr/local/lib/python3.6/site-packages/pandas/core/reshape/merge.py", line 546, in __init__
    self._validate_specification()
  File "/usr/local/lib/python3.6/site-packages/pandas/core/reshape/merge.py", line 1059, in _validate_specification
    if len(self.right_on) != len(self.left_on):
TypeError: object of type 'NoneType' has no len()

temp_merged_data sample:

   mac_address  device_id device_type     ip_address      port  vlan
0000.001d.f805        304      Switch    10.10.10.1      None   5.0
0000.001d.f10a         89      Router  10.10.10.129      None   10.0
0000.001d.f0a3         89      Router  10.10.10.193      None   15.0
0000.001d.f024        303      Switch  10.10.10.225     Gi0/23  20.0
0101.001d.79a2        303      Switch   10.10.10.26     Gi0/3   5.0

desc_data sample:

                description  device_id device_type mac_address      port
    *** UPLINK to SW-03 ***        303      Switch                Gi0/23
       *** UPLINK to SW ***        303      Switch                Gi0/24
               *** CCTV ***        304      Switch                Gi0/21
    *** UPLINK to SW-03 ***        304      Switch                Gi0/23
       *** UPLINK to SW ***        304      Switch                Gi0/24

I want to be able to merge the port description into the temp_mergedata frame if it exists, if it doesnt leave the original data as is.

Thanks

you might have to specify the right_on as well. It is evident from the error msg — mad_
– mad_, Commented Jul 24, 2018 at 17:08

mad_ · Accepted Answer · 2018-07-24 17:24:38Z

3

host_data = temp_merged_data.merge(desc_data, left_on=['device_id', 'port'], how='left', right_on=['device_id', 'port'])

Or as suggested by @Scott If field list is same

host_data = temp_merged_data.merge(desc_data, on=['device_id', 'port'], how='left')

edited Jul 24, 2018 at 17:24

answered Jul 24, 2018 at 17:10

mad_

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2 Comments

Scott Boston Over a year ago

If left_on is the same as right_on just use on.

mad_ Over a year ago

Thanks @ScottBoston

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