Changing date format of csv headers.

header_date_cleanup.py

# From a list of bad dates:
import csv
from datetime import datetime

input_file = "bad_dates.csv"
output_file = "good_dates.csv"
with open(output_file, 'wb') as open_file:
	writer = csv.writer(open_file, dialect='excel')
	with open(input_file, 'rU') as csvfile:
		reader = csv.DictReader(csvfile)
		for row in csvreader:
			bad_dt = row['date']
			bad_dt = datetime.strptime(bad_dt, "%m%d%Y")
			good_dt = datetime.strftime(bad_dt, "%Y%m%d")
			writer.writerow( [good_dt] )

# To work with the original file:
import csv
from datetime import datetime

input_file = "bad_dates2.csv"
output_file = "good_dates2.csv"
with open(input_file, 'rU') as csvfile:
	reader = csv.DictReader(csvfile)
	new_names = []
	index = -1
	for fn in reader.fieldnames:
		index += 1
		try:
			bad_dt = datetime.strptime(fn, "%m%d%Y")
			fn = datetime.strftime(bad_dt, "%Y%m%d")
			reader.fieldnames[index] = fn
		except ValueError as e:
			reader.fieldnames[index] = fn
		reader.fieldnames[0:3] = ('Site', 'Latitude', 'Longitude')
	with open(output_file, 'wb') as open_file:
		writer = csv.DictWriter(open_file, fieldnames = reader.fieldnames)
		writer.writeheader()
		for row in reader:
			writer.writerow(row)
			
# Notice that at the bottom, unlike the last csv writing that we did, here we 
# are using csv.DictWriter. Dictionaries in Python are not ordered, that is, 
# when you print out a dictionary, you just get a list in alphabetical or 
# numerical order. Using DictWriter here will however, allow Python to write our 
# csv in the correct order, because Python maps each value in the csv file to 
# the correct header in the dictionary that was created in DictReader.