Merging two CSV files by a common column python

Question

I am trying to merge two csv files with a common id column and write the merge to a new file. I have tried the following but it is giving me an error -

import c         


        

Answer 1

Here is an example using pandas

import sys
from StringIO import StringIO
import pandas as pd

TESTDATA=StringIO("""DOB;First;Last
    2016-07-26;John;smith
    2016-07-27;Mathew;George
    2016-07-28;Aryan;Singh
    2016-07-29;Ella;Gayau
    """)

list1 = pd.read_csv(TESTDATA, sep=";")

TESTDATA=StringIO("""Date of Birth;Patient First Name;Patient Last Name
    2016-07-26;John;smith
    2016-07-27;Mathew;XXX
    2016-07-28;Aryan;Singh
    2016-07-20;Ella;Gayau
    """)


list2 = pd.read_csv(TESTDATA, sep=";")

print list2
print list1

common = pd.merge(list1, list2, how='left', left_on=['Last', 'First', 'DOB'], right_on=['Patient Last Name', 'Patient First Name', 'Date of Birth']).dropna()
print common

Answer 2

Thanks Shijo.

This is what worked for me after - merged by the first column in each csv.

import csv
from collections import OrderedDict

with open('stops.csv', 'rb') as f:
    r = csv.reader(f)
    dict2 = {row[0]: row[1:] for row in r}

with open('stops2.csv', 'rb') as f:
    r = csv.reader(f)
    dict1 = OrderedDict((row[0], row[1:]) for row in r)

result = OrderedDict()
for d in (dict1, dict2):
    for key, value in d.iteritems():
         result.setdefault(key, []).extend(value)

with open('ab_combined.csv', 'wb') as f:
    w = csv.writer(f)
    for key, value in result.iteritems():
        w.writerow([key] + value)