Question

f = open("file1.csv", "r")
g = open("file2.csv", "w")

a = csv.reader(f, delimiter=";", skipinitialspace=True)
b = csv.writer(g, delimiter=";")

for line in a:
    b.writerow(line)

In the above code, I try to load file1.csv using the csv module in Python2.7, and then write it in file2.csv using a csv.writer.

My issue comes from existing whitespaces (a single space character) after the delimiter in the input file. I need to remove them in order to do some data manipulation later on, so I used the skipinitialspace=True argument for the reader. However, I cannot get the writer to print the space char after the delimiter, and therefore disturbing any subsequent diffing of the two files.

I tried to use the Sniffer class to auto-generate a Dialect but I guess my input files (coming from a large complex legacy system, with dozens of fields and poor quoting and escaping) are proving to be too complex for this.

In more simple terms I’m looking for the answers to the following questions:

• How can I insert a space character after each delimiter in the writer?
• Incidently, what are the reasons to prohibit the use of multi-character strings as delimiters? delimiter="; " would’ve solved my problem.

Answer 1

You can wrap your file objects in proxies that add the whitespace:

>>> class DelimitedFile(file):
...     def write(self, value):
...             super(DelimitedFile, self).write(value.replace(";", "; "))
... 
>>> f = DelimitedFile("foo", "w")
>>> f.write("hello;world")
>>> f.close()
>>> open("foo").read()
'hello; world'