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Python

Posted by Evan Dix
Evan Dix
1,597 Points

Writing quotes around strings to CSVs in Python

I was following the guide here to learn about writing to CSV files. https://teamtreehouse.com/library/csv-and-json-in-python

I grabbed an example CSV file from the internet and it is as follows: 

"Name","Sex","Age","Height (in)","Weight (lbs)"
"Alex","M",41,74,170
"Bert","M",42,68,166
"Carl","M",32,70,155
"Dave","M",39,72,167

After following the guide, I am able to write to the file using the following code:

def write():
    with open("stats.csv", "a") as file:
        fieldnames = ["Name","Sex","Age","Height (in)","Weight (lbs)"]
        writer = csv.DictWriter(file, fieldnames=fieldnames)
        writer.writerow({
            "Name": "Bill",
            "Sex": "M",
            "Age": 19,
            "Height (in)": 102,
            "Weight (lbs)": 234
        })
    pass

if __name__ == "__main__":
    #read()
    write()

However, my output now looks like this:

"Name","Sex","Age","Height (in)","Weight (lbs)"
"Alex","M",41,74,170
"Bert","M",42,68,166
"Carl","M",32,70,155
"Dave","M",39,72,167
Bill,M,19,102,234

I want to make sure my code writes the quotes around the strings. I figured out this way works, but I can't understand why:

def write():
    with open("stats.csv", "a") as file:
        fieldnames = ["Name","Sex","Age","Height (in)","Weight (lbs)"]
        writer = csv.DictWriter(file, fieldnames=fieldnames, quotechar=" ")
        writer.writerow({
            "Name": "\"Bill\"",
            "Sex": "\"M\"",
            "Age": 18,
            "Height (in)": 102,
            "Weight (lbs)": 234
        })
    pass

if __name__ == "__main__":
    #read()
    write()

After researching the quotechar parameter, it is still unclear to my why a "space" would work here. Without this quotechar parameter, my output looks like this. Using double quotes as '" string "' also does the same weird tripple quote thing:

"Name","Sex","Age","Height (in)","Weight (lbs)"
"Alex","M",41,74,170
"Bert","M",42,68,166
"Carl","M",32,70,155
"Dave","M",39,72,167

"Bill","M",18,102,234

"""Bill""","""M""",18,102,234

So if anyone can offer some advice or insight into this behavior that would be great. Also, it keeps creating a new line every time I run it. If you also have any idea about that it would be great. Thank you!

Evan Dix
Evan Dix
1,597 Points

I have resolved the issue by using the following code:

import csv

dictionary = [{"Name":"Alex","Sex":"M","Age":41,"Height (in)":74,"Weight (lbs)":170},
        {"Name":"Bert","Sex":"M","Age":41,"Height (in)":74,"Weight (lbs)":170},
        {"Name":"Card","Sex":"M","Age":41,"Height (in)":74,"Weight (lbs)":170},
        {"Name":"Dave","Sex":"M","Age":41,"Height (in)":74,"Weight (lbs)":170}]


def write():
    with open("stats.csv", "a") as file:
        fieldnames = ["Name","Sex","Age","Height (in)","Weight (lbs)"]
        writer = csv.DictWriter(file, delimiter=",", fieldnames=fieldnames, quoting=csv.QUOTE_STRINGS, lineterminator="\n")
        for line in dictionary:   
             #print(line["Name"]) 
            writer.writerow(line)      
write()

Output is as follows: 

"Name","Sex","Age","Height (in)","Weight (lbs)"
"Alex","M",41,74,170
"Bert","M",42,68,166
"Carl","M",32,70,155
"Dave","M",39,72,167
"Alex","M",41,74,170
"Bert","M",41,74,170
"Alex","M",41,74,170
"Bert","M",41,74,170
"Card","M",41,74,170
"Dave","M",41,74,170

The key changes were adding the quoting=csv.QUOTE_STRINGS and lineterminator="\n" parameters to the CSV DictWriter.

However, I am still intersted to learn why this example from my first post worked. Specifically, why quotechar=" " and "\" string \"" worked together to product the desired output.

def write():
    with open("stats.csv", "a") as file:
        fieldnames = ["Name","Sex","Age","Height (in)","Weight (lbs)"]
        writer = csv.DictWriter(file, fieldnames=fieldnames, quotechar=" ")
        writer.writerow({
            "Name": "\"Bill\"",
            "Sex": "\"M\"",
            "Age": 18,
            "Height (in)": 102,
            "Weight (lbs)": 234
        })
    pass

if __name__ == "__main__":
    #read()
    write()

If you have any insight please let me know!

1 Answer

Jeff Muday
MOD
Jeff Muday
Treehouse Moderator 28,720 Points
Jeff Muday
Jeff Muday
Treehouse Moderator 28,720 Points

I am glad you solved your problem. You might want to consult the documentation regarding the csv reader/writer packages. This would help you write it a bit more efficiently.

For example you might have chosen to take advantage of the writer.writeheader() function which would have saved you a little bit of typing.

Also... probably want to look into quotechar and delimiter which would allow you to get around any possible confusion in the code.

https://docs.python.org/3/library/csv.html