CSV - Writing
Writing to a CSV file
You can write data using the writerows() method of the csv.writer object which writes multiple rows in one go.
data = [["name", "faculty", "department"], ["Davies", "Eng", "EEE"],
["Smith", "Eng", "Computing"]]
with open("uni.csv", "w") as csv_file:
writer = csv.writer(csv_file)
writer.writerows(data)
The content of the new uni.csv should look like this:
name,faculty,department
Davies,Eng,EEE
Smith,Eng,Computing
You can also add a new (single) row to the CSV we generated using the .writerow() method.
row = ["Williams", "Eng", "EEE"]
with open("uni.csv", "a") as csv_file: # Note append mode "a"
writer = csv.writer(csv_file)
writer.writerow(row)
The content of uni.csv now looks like this:
name,faculty,department
Davies,Eng,EEE
Smith,Eng,Computing
Williams,Eng,EEE
You can also modify existing rows.
row = ["Williams", "Eng", "ChemEng"]
# Read existing rows
with open("uni.csv") as csv_file:
csv_reader = csv.reader(csv_file)
rows = list(csv_reader)
# Replace last row
rows[3] = row
# Save CSV with new record
with open("uni.csv", "w") as csv_file:
writer = csv.writer(csv_file)
writer.writerows(rows)
The content of uni.csv now looks like this:
name,faculty,department
Davies,Eng,EEE
Smith,Eng,Computing
Williams,Eng,ChemEng
Writing to CSV files from a dictionary
You can also write to a CSV file from a dictionary.
Writing a single row (this code demonstrates a CSV separated by |).
with open("uni.csv", "w") as csv_file:
fieldnames = ["name", "faculty", "dept"]
writer = csv.DictWriter(csv_file, fieldnames=fieldnames, delimiter="|")
writer.writeheader()
writer.writerow({"name": "Davies", "faculty": "Eng", "dept": "EEE"})
writer.writerow({"name": "Smith", "faculty": "Eng", "dept": "Computing"})
The output uni.csv file is:
name|faculty|dept
Davies|Eng|EEE
Smith|Eng|Computing
You can also dump a whole dictionary into a CSV file.
data = [{"name": "Davies", "faculty": "Eng", "dept": "EEE"},
{"name": "Smith", "faculty": "Eng", "dept": "Comp"}
]
with open("uni.csv", "w") as csv_file:
fieldnames = ["name", "faculty", "dept"]
writer = csv.DictWriter(csv_file, fieldnames=fieldnames, delimiter="|")
writer.writeheader()
writer.writerows(data)
And the output uni.csv file:
name|faculty|dept
Davies|Eng|EEE
Smith|Eng|Comp