Something not quite right with application of CSV Module in Python

Question

I have a string that I am trying to write to file where the data has the following format:

100.10 89.7 1,891.43 123.99 

Which I want converting to the following format:

"100.10","89.7","1,891.43","123.99", 

However using the following code (where filepath is defined earlier in the code as a text file location and data2 is a string:

csv.register_dialect('sas', delimiter=',',quoting=csv.QUOTE_ALL)

with open(filepath, "w") as f:
    writer = csv.writer(f, dialect='sas')
    writer.writerow(data2)

I am getting this output:

 "1","0","0",".",1,"0","8","9",".","7","1","8","9","1",".","4","3","1","2","3",".","9","9", 

I want to use quotes to mask the presence of possible commas in the data, what am I doing wrong?

Answer 1

You are passing a string to writerow , so it iterates over characters, putting a comma between each one. The minimal fix is:

writer.writerow(data2.split(" "))

Alternatively, it is probably more convenient to keep the data in a list rather than making a string in the first place!

Answer 2

my_string = '100.10 89.7 1891.43 123.99'

string_list = my_string.split()

And string_list returns:

['100.10', '89.7', '1891.43', '123.99']

When you do:

csv.register_dialect('sas', delimiter=',',quoting=csv.QUOTE_ALL)

with open(filepath, "w") as f:
    writer = csv.writer(f, dialect='sas')
    writer.writerow(data2)

It's splitting data2 by character, so when you read it back in it's reading each character as a separate column. You probably want this:

csv.register_dialect('sas', delimiter=',',quoting=csv.QUOTE_ALL)

with open(filepath, "w") as f:
    writer = csv.writer(f, dialect='sas')
    writer.writerow(data2.split())

Edit

So I might suggest a different tack, forget about registering a dialect, for me that has always been problematic anyways.

string_list = ['100.10', '89.7', '1,891.43', '123.99']
with open(filepath, 'w') as f:
    writer = csv.writer(f, quoting=csv.QUOTE_ALL)
    writer.writerow(string_list)

with open(filepath, 'r') as f:
    print f.read()

For me printed:

"100.10","89.7","1,891.43","123.99"

And

with open(filepath, 'rU') as f:
    reader = csv.reader(f, quoting=csv.QUOTE_ALL)
    data = next(reader) # next(reader) gives us the iterable's first row.

data

returns:

['100.10', '89.7', '1,891.43', '123.99']

So when you write, do this:

with open(filepath, "w") as f:
    writer = csv.writer(f, quoting=csv.QUOTE_ALL)
    writer.writerow(data2.split()) # *write here

You are probably intending to write a bunch of rows, so be sure to either loop through your rows that you want to write, or use writerows instead of writerow . See the examples in the documentation.