Combining several dataframe results with for Loop in Python Pandas

Question

Lets say I have these functions:

def query():
    dict = (
             { "NO" : 1, "PART" : "ALPHA" }, 
             { "NO" : 2, "PART" : "BETA" }
           )
    finalqueryresult = pandas.DataFrame()

    for info in dict: #I use this loop to request query depends on the dict data, in this example twice (2 records from dict)
         finalqueryresult.append( sendquery(info["NO"], info["PART"]) )

def sendquery( no, part):
     *some code to request query to server and save it under reqresult variable*
     *.....*
     *.....*
     return reqresult

For example above, when sending first query (record with "NO" = 1) it will return: (lets say this is df1)

  NAME  COUNTRY
1  RYO   JPN
2  JON   NZ

and the last query (record with "NO" = 2): (lets say this df2)

   NAME    COUNTRY
1  TING      CN
2  ASHYU     INA

and what I want is finalqueryresult will be like this: (df1 combined with df2):

  NAME     COUNTRY
1 RYO        JPN
2 JON        NZ
3 TING       CN
4 ASHYU      INA

But I failed, the finalqueryresult is always empty. I suppose something is wrong with this:

for info in dict:
     finalqueryresult.append( sendquery(info["NO"], info["PART"]) )

jezrael · Accepted Answer · 2016-04-21 09:20:05Z

2

I think you need first append all DataFrames to list dfs and then use concat:

dfs= []
for info in dict:
     #sendquery(info["NO"], info["PART"] return DataFrame
     dfs.append( sendquery(info["NO"], info["PART"]) )

finalqueryresult = pd.concat(dfs, ignore_index=True)

edited Apr 21, 2016 at 9:20

answered Apr 21, 2016 at 9:12

jezrael

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2 Comments

jrjc Over a year ago

nice ! I didn't know about the ignore_index argument.

jezrael Over a year ago

Glad can help you! Good luck!

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