[Tutor] Is there a way to use "with" across suite boundaries?

Sat May 23 08:55:06 CEST 2015

Jim Mooney Py3.4.3winXP wrote:

> '''I was using with open...:, but I'm printing a header in one function,
> calling a looping
> function to print detail lines, then returning to the calling function to
> print
> the footer. But that didn't work since the with statement only seems to
> work with the lexical suite and the file wasn't open in the detail print
> function. Is there
> a way around this, other than passing the file as I have here? Also, is it
> a good idea to pass a file handle like that or is there a better way?

Something else must have gone wrong as

def make_lines():
    with open('co2-sample.csv') as co2:
        with open('output.html', 'w') as ht:
            linelist = []
            print(htbegin, file=ht)
            for line in co2:
                newlist = line.rsplit(',', 5)
                for token in newlist:
                    linelist.append(token.strip('"'))
                    linelist[-1] = linelist[-1].strip()
                fprint(linelist, ht)
                linelist = []
            print(htend, file=ht)

should run without error. Also possible:

    with open('co2-sample.csv') as co2, open('output.html', 'w') as ht:
        ...

But may I suggest that you delegate parsing the CSV to the standard library? 
Then you can write

import csv

def make_lines():
    with open('co2-sample.csv') as co2:
        rows = csv.reader(co2)
        with open('output.html', 'w') as ht:
            print(htbegin, file=ht)
            for linelist in rows:
                fprint(linelist, ht)
            print(htend, file=ht)

> Using the below csv file  co2-sample.csv  to print a simple HTML table
> (header omitted)
> Since this is a file there are enclosing single quotes not visible:
> 
> "ANTIGUA AND BARBUDA",0,0,0,0,0
> "ARGENTINA",37,35,33,36,39
> "BAHAMAS, THE",1,1,1,1,1
> "BAHRAIN",5,6,6,6,6
> "SPANISH INQUISITION, THE, SILLY",10,33,14,2,8
> 
> Program follows (py3.4, winxp):'''
> 
> htbegin = '''
> <html>
> <head>
> <title>htest</title>
> <style>
> table, td {border:2px solid black; border-collapse:collapse;}
> td {padding:3px; background-color:pink;
> text-align:right;font-family:verdana;}
> td.l {text-align:left}
> </style>
> 
> </head>
> <body>
> <table>
> '''
> 
> htend = '''
> </table>
> </body>
> </html>
> '''
> 
> def make_lines():
>     co2 = open('co2-sample.csv')
>     ht = open('output.html', 'w')
>     linelist = []
>     print(htbegin, file=ht)
>     for line in co2:
>         newlist = line.rsplit(',', 5) # ending is regular so split it out
> first
>         for token in newlist:         # since split char inside quotes for
> nation is problematic
>             linelist.append(token.strip('"')) # get rid of extra quotes
>             linelist[-1] = linelist[-1].strip()
>         fprint(linelist, ht)
>         linelist = []
>     co2.close()
>     print(htend, file=ht)
>     ht.close()
> 
> 
> def fprint(linelist, ht):
>     # size formatting irrelevant for HTML
>     formatted_string = "<td
> 
class=l>{}</td><td>{}</td><td>{}</td><td>{}</td><td>{}</td><td>{}</td>".format(*linelist)
>     print(formatted_string, file=ht)
>     print('</tr>', file=ht)
> 
> 
> if __name__ == "__main__":
>     make_lines()