My first ever Python program, comments welcome

Ivan@work ivan.cvetkovic at pakel.hr
Mon Jul 23 09:12:02 CEST 2012


On 21.07.2012 21:08, Lipska the Kat wrote:
> Greetings Pythoners
>
> A short while back I posted a message that described a task I had set
> myself. I wanted to implement the following bash shell script in Python
>
> Here's the script
>
> sort -nr $1 | head -${2:-10}
>
> this script takes a filename and an optional number of lines to display
> and sorts the lines in numerical order, printing them to standard out.
> if no optional number of lines are input the script prints 10 lines
>
> Here's the file.
>
> 50    Parrots
> 12    Storage Jars
> 6    Lemon Currys
> 2    Pythons
> 14    Spam Fritters
> 23    Flying Circuses
> 1    Meaning Of Life
> 123    Holy Grails
> 76    Secret Policemans Balls
> 8    Something Completely Differents
> 12    Lives of Brian
> 49    Spatulas
>
>
> ... and here's my very first attempt at a Python program
> I'd be interested to know what you think, you can't hurt my feelings
> just be brutal (but fair). There is very little error checking as you
> can see and I'm sure you can crash the program easily.
> 'Better' implementations most welcome
>
> #! /usr/bin/env python3.2
>
> import fileinput
> from sys import argv
> from operator import itemgetter
>
> l=[]

You can do without this, see below.

> t = tuple

This initialization does nothing. Assignment t=(line.split('\t')) makes 
`t` a list (not a tuple), discarding any previous value. And you don't 
really need t:

> with fileinput.input(files=(filename)) as f:
>      for line in f:
>          t=(line.split('\t'))
>          t[0]=int(t[0])
>          l.append(t)

List comprehension is your friend, and now you don't need to initialize 
l to an empty list.

with open(filename) as f:
     l = [line.split('\t') for line in f]

The first element of each row is now a string, but it's easy to fix:

>      l=sorted(l, key=itemgetter(0))

Use in-place sorting and cast the sorting element to int

l.sort(key=lambda t: int(t[0]))


>          inCount = int(argv[2])
>          lineCount = inCount

lineCount = int(argv[2]) works just fine


>
>      for c in range(lineCount):
>          t=l[c]
>          print(t[0], t[1], sep='\t', end='')

Whenever you write "for i in range(n)" you're (probably) doing it wrong. 
Here you can use list slicing, and as a bonus the program doesn't bomb 
when lineCount is greater than length(l)

for t in l[:lineCount]:
     print(t[0], t[1], sep='\t', end='')



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