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+--- Thread: match type with value in csv parsing function (/thread-36143.html)
match type with value in csv parsing function - vinci - Jan-20-2022
Hello,
In the following code I do some parsing of files (csv):
#!/usr/bin/env python3
import csv
def parse_csv(filename, select=None, types=None):
'''
Parse a CSV file into a list of records
'''
with open(filename) as f:
rows = csv.reader(f)
# Read the file headers
headers = next(rows)
if select:
indices = [ headers.index(colname) for colname in select ]
headers = select
else:
indices = []
records = []
for row in rows:
if not row: # Skip rows with no data
continue
# Filter the row if specific columns were selected
if indices:
row = [ row[index] for index in indices ]
if types:
row = [ func(row) for func, val in zip(types, row) ]
record = dict(zip(headers, row))
records.append(record)
return records
shares_held = parse_csv('../Data/portfoliodate.csv', select=['name', 'time'], types=[str, str])
print(shares_held)My question is related to this sentence:row = [ func(row) for func, val in zip(types, row) ]Is matching
types with row essential here? If I replace it with this:row = [ func(row) for func in types ]the code seems to be behave identically, because you have to match the type and values anyway when calling the function (
types=[str, str] ), otherwise it errors out.Looking forward to your answers :)
RE: match type with value in csv parsing function - vinci - Jan-21-2022
What I've understood thus far is that this wouldn't/shouldn't work:
row = [ func(row) for func in types ]I am applying the function (str) to the entire list and it doesn't make sense. Whereas iterating over the list should work.
The reason why I thought it was behaving differently was that I didn't actually test it correctly. Applying str on a list works, but applying anything else doesn't. And I was trying to test it by changing str to int (for a date format), and it didn't work and I thought this was expected behaviour, but I hadn't properly test int/float which wouldn't have worked either way.
RE: match type with value in csv parsing function - Larz60+ - Jan-21-2022
please post sample (small) csv file