Python script to update an existing column values in a csv from another two tables

Question

I need to update two columns: feedID and OperatID of table#1.csv with 'feed description', 'Operate description' from other CSV files. I don't have the pandas module available.

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import csv
table1 = r'N:\Extracts\table1.csv'
table2 = r'N:\Extracts\table2.csv'
with open(table1,'r+')as f1:
 f1reader = csv.reader(f1)
 f1reader.next()
 f1writer = csv.writer(f1)
 for row in f1reader:
 in_fdrid = row[2]
 def get_fdrname(in_fdrid):
 with open(table2,'rU')as f2:
 f2reader = csv.reader(f2)
 for f2row in f2reader:
 if in_fdrid == f2row[1]:
 fdrnm = f2row[2]
 return fdrnm
 f2.close()
 row[2].replace(in_fdrid,get_fdrname(in_fdrid))

• user157778: I just added the script that I was using to replace. no error and table not updated. Was tried to updated first one column since i just started python and don't have any prior coding experience.

Answer 1

Your code as it stands now will open and read file f2 every time you process a line from f1. This is way more work than you need to do.

I suggest you create a dictionary mapping ids to replacement values. You can then read all the lines from table2 one time, and populate the dictionary:

feed_desc = dict()
with open(table2) as tbl2:
 t2csv = csv.reader(tbl2)
 next(t2csv) # skip headings
 for t2row in t2csv:
 feed_id = t2row[1]
 desc = t2row[2]
 feed_desc[feed_id] = desc

Once that is done, you can simply check if an id is in feed_desc, and if so provide the replacement value:

with ...
 ...
 for t1row in t1csv:
 feed_id = t1row[2]
 if feed_id in feed_desc:
 t1row[2] = feed_desc # replace id with desc, you said.
 t1writer.writerow(t1row)

You can do a similar thing for t3 into a different dictionary. Just make sure you read both t2 and t3 before you start processing t1.