[Tutor] write dictionary to file

[Ian D]

Ok I used :


spamwriter.writerow({'user':email,'first':row['first'],'last':row['last'], 'password':row['password'] })


Seems to be almost finished thanks

----------------------------------------
> From: duxbuz at hotmail.com
> To: tutor at python.org
> Date: Mon, 23 Jun 2014 09:17:44 +0000
> Subject: Re: [Tutor] write dictionary to file
>
>
>>>
>>> import csv
>>>
>>> csvfile= open('StudentListToSort.csv', newline='')
>>> spamreader = csv.DictReader(csvfile,delimiter=',',quotechar='|')
>>
>> Are you sure that your input file uses | as a quote character and , as
>> the field delimiter?
>
>
> No I overlooked this
>
>
>>
>>
>>> #open a file to write to later
>>> fields = ['user','first','last','password','year']
>>> csvoutput = open('output.csv', 'wb+')
>>
>> I'm pretty sure you don't want to use "wb+" mode. Since you're using
>> Python 3, I think you should just use "w" mode.
>>
>> The "b" turns on binary mode, and in Python 3 you don't want that. The
>> "+" turns on either "read/write" mode or "append" mode, I don't remember
>> which, but either way I don't think it's necessary for what you are
>> doing.
>
>
> Yes I came across this python 3 idiosyncrasy
>
>
>
>>
>>
>>> spamwriter = csv.DictWriter(csvoutput,fieldnames=fields, delimiter=' ')
>>
>> Now you're turning every , delimiter into a space. Are you sure you want
>> that?
>>
>>
>
>
> Overlooked this
>
>
>
>>> for row in spamreader:
>>> if row['year'] == '40':
>>> username = row['user']
>>> email = "".join([username,'@email.com])
>>
>> Syntax error: you left out the closing single quote. You need:
>>
>> email = "".join([username,'@email.com'])
>>
>
>
> I think I may have messed that up editing code for public viewing.
>
>
>
>
> On to your example.....
>
>
>
>>
>> import csv
>>
>> # Open the file we're reading from.
>> csvfile= open('StudentListToSort.csv', newline='')
>> # Open a file to write to.
>> csvoutput = open('output.csv', 'w', newline='')
>>
>> fields = ['user', 'first', 'last', 'password', 'year']
>>
>> # Are you sure you want | as the quote character?
>> spamreader = csv.DictReader(csvfile, delimiter=',', quotechar='|')
>
>>
>>
>> # Still using , as a delimiter, not space.
>> spamwriter = csv.DictWriter(csvoutput, fieldnames=fields, delimiter=',')
>>
>> for row in spamreader:
>> if row['year'] == '40':
>> email = row['user'] + '@email.com'
>> output = [ row[fieldname] for fieldname in fields ]
>
>
> I am unsure about this syntax [ row[fieldname] for fieldname in fields ]
>
>
>
> The FOR loop is not in any context I have used before. I have seen examples(recently) so its obviously standard practice, but not something I would ever think to type.
>
>
>
>> print(output)
>> # DictWriter needs a dict, not a list.
>> spamwriter.writerow({name: row[name] for name in fields})
>> print("Warning: email calculated but never used:", email)
>
>
>
>
> And this writerow syntax is something new for me, as are dictionaries( which I have tried to read up and understand.)
>
>
>
>>spamwriter.writerow({name: row[name] for name in fields})
>
>
>
> This looks like the same loop as the one above but a dictionary using curly braces(for dict), its the same unfamiliar way of writing a FOR loop for me.
>
>
>
>
> So if I wanted multiple rows in the output csv file I would try:
>
>
> ({name: row[name], row[email, row[first] for name in fields})
>
>
> which doesn't work as the syntax is invalid, so what would I need to change to allow spamwriter.writerow to generate multiple fields?
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