Pythonically add header to a csv file
I wrote a Python script merging two csv files, and now I want to add a header to the final csv. I tried following the suggestions reported here and I got the following error: expected string, float found
. What is the most pythonic way to fix this?
Here is the code I am using:
import csv
with open('combined_file.csv', 'w', newline='') as outcsv:
writer = csv.DictWriter(outcsv, fieldnames = ["Date", "temperature 1", "Temperature 2"])
writer.writeheader()
with open('t1.csv', 'r', newline='') as incsv:
reader = csv.reader(incsv)
writer.writerows(row + [0.0] for row in reader)
with open('t2.csv', 'r', newline='') as incsv:
reader = csv.reader(incsv)
writer.writerows(row[:1] + [0.0] + row[1:] for row in reader)
Solution 1:
The DictWriter()
class expects dictionaries for each row. If all you wanted to do was write an initial header, use a regular csv.writer()
and pass in a simple row for the header:
import csv
with open('combined_file.csv', 'w', newline='') as outcsv:
writer = csv.writer(outcsv)
writer.writerow(["Date", "temperature 1", "Temperature 2"])
with open('t1.csv', 'r', newline='') as incsv:
reader = csv.reader(incsv)
writer.writerows(row + [0.0] for row in reader)
with open('t2.csv', 'r', newline='') as incsv:
reader = csv.reader(incsv)
writer.writerows(row[:1] + [0.0] + row[1:] for row in reader)
The alternative would be to generate dictionaries when copying across your data:
import csv
with open('combined_file.csv', 'w', newline='') as outcsv:
writer = csv.DictWriter(outcsv, fieldnames = ["Date", "temperature 1", "Temperature 2"])
writer.writeheader()
with open('t1.csv', 'r', newline='') as incsv:
reader = csv.reader(incsv)
writer.writerows({'Date': row[0], 'temperature 1': row[1], 'temperature 2': 0.0} for row in reader)
with open('t2.csv', 'r', newline='') as incsv:
reader = csv.reader(incsv)
writer.writerows({'Date': row[0], 'temperature 1': 0.0, 'temperature 2': row[1]} for row in reader)
Solution 2:
You just add one additional row before you execute the loop. This row contains your CSV file header name.
schema = ['a','b','c','b']
row = 4
generators = ['A','B','C','D']
with open('test.csv','wb') as csvfile:
writer = csv.writer(csvfile, delimiter=delimiter)
# Gives the header name row into csv
writer.writerow([g for g in schema])
#Data add in csv file
for x in xrange(rows):
writer.writerow([g() for g in generators])
Solution 3:
This worked for me.
header = ['row1', 'row2', 'row3']
some_list = [1, 2, 3]
with open('test.csv', 'wt', newline ='') as file:
writer = csv.writer(file, delimiter=',')
writer.writerow(i for i in header)
for j in some_list:
writer.writerow(j)