Many tutorials on writing csv files have the mode set to 'wb', why?
python
Solution
It's necessary to use the mode `"wb"` when writing output using the `csv` module on Windows, because the `csv` module will write out line-ends as `\r\n` regardless of what platform you're running on.
If you're running on Windows, and you have a file open with mode `"w"`, Python will add an extra carriage return every time you write a newline. So if you use a file with mode `"w"` to write output using the `csv` module, you will end up with `\r\r\n` line-endings, as both Python and the `csv` module have added carriage-return characters.
Here's a quick program that demonstrates the result. Note that we read the file in binary mode (`"rb"`) to prevent Python from replacing `\r\n` with `\n` as it reads the file back in:
import csv
with open("output.csv", "w") as f:
w = csv.writer(f)
w.writerow([1,2,3,4])
w.writerow([5,6,7,8])
with open("output.csv", "rb") as f:
print repr(f.read())
When I run this on Windows, I get the following output:
'1,2,3,4\r\r\n5,6,7,8\r\r\n'
Problem
For example: Writing to csv file in Python ``` with open('StockPrice.csv', 'wb') as f: ``` Why would we need to open in binary for a csv file? Is this just habit, or is there a use-case for when binary is necessary for a csv file?