Python 3.3 CSV.Writer writes extra blank rows
csv, python, python-3.x
Solution
The `'wb'` mode was OK for Python 2. However, it is wrong in Python 3. In Python 3, the csv reader needs strings, not bytes. This way, you have to open it in text mode. However, the `\n` must not be interpreted when reading the content. This way, you have to pass `newline=''` when opening the file:
with open("./files/forest.csv", newline='') as input_file \
open('something_else.csv', 'w', newline='') as output_file:
writer = csv.writer(output_file)
...
If the file is not pure ASCII, you should also consider to add the `encoding=...` parameter.
Problem
Using Python 3.3 on Windows 8, when writing to a CSV file, I get the error `TypeError: 'str' does not support the buffer interface` and `"wb"` flag was used. However when only the `"w"` flag was used, I get no errors, but every row is separated by a blank row! Problem Writing Code ``` test_file_object = csv.reader( open("./files/test.csv", 'r') ) next(test_file_object ) with open("./files/forest.csv", 'wb') as myfile: open_file_object = csv.writer( open("./files/forest.csv", 'wb') ) i = 0 for row in test_file_object: row.insert(0, output[i].astype(np.uint8)) open_file_object.writerow(row) i += 1 ``` Error ``` --------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-121-8cbb94f602a8> in <module>() 8 for row in test_file_object: 9 row.insert(0, output[i].astype(np.uint8)) ---> 10 open_file_object.writerow(row) 11 i += 1 TypeError: 'str' does not support the buffer interface ``` Problem Reading When reading, I cant seem to use the `"rb"` flags so it will give the error `iterator should return strings, not bytes` when trying to ignore the first row (headers). Code ``` csv_file_object = csv.reader(open('files/train.csv', 'rb')) header = next(csv_file_object) train_data = [] for row in csv_file_object: train_data.append(row) train_data = np.array(train_data) ``` Error ``` Error Traceback (most recent call last) <ipython-input-10-8b13d1956432> in <module>() 1 csv_file_object = csv.reader(open('files/train.csv', 'rb')) ----> 2 header = next(csv_file_object) 3 train_data = [] 4 for row in csv_file_object: 5 train_data.append(row) Error: iterator should return strings, not bytes (did you open the file in text mode?) ```