[Tutor] string to list

Eike Welk eike.welk at gmx.net
Wed Feb 10 15:24:46 CET 2010

On Wednesday February 10 2010 14:32:52 Owain Clarke wrote:
> My son was doing a statistics project in which he had to sort some data by
>  either one of two sets of numbers, representing armspan and height of a
>  group of children - a boring and painstaking job.  I came across this
>  piece of code:-
> li=[[2,6],[1,3],[5,4]]  # would also work with li=[(2,6),(1,3),(5,4)]
> li.sort(key=lambda x:x[1] )
> print li
> It occurred to me that I could adapt this so that he could input his data
>  at the command line and then sort by x:x[0] or x:x[1].  And I have not
>  discovered a way of inputting a list, only strings or various number
>  types.

I would let him enter the data into the program text directly, or parse a text 
file with a simple format. Something like:

in_data = [
#arm span, height
[2       , 6 ],
[1       , 3 ],
[5       , 4 ],
[       ,  ],
[       ,  ],
[       ,  ],

This way the computation can be repeated when there were errors int the data. 
Otherwise one error might spoil all the work he did while typing in the data. 
Designing a simple text representation of the data and interpreting it with a 
computer program, is much more easy that writing good user interfaces. 

For the same reason Unix, a concept from the late 1960s, is still doing 
relatively well.   


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