turn list of letters into an array of integers

[88888 Dihedral]

Chris Rebert於 2012年10月24日星期三UTC+8下午2時07分29秒寫道：
> On Tue, Oct 23, 2012 at 10:23 PM, seektime <michael.j.krause at gmail.com> wrote:
> 
> > Here's some example code. The input is a list which is a "matrix" of letters:
> 
> >    a  b  a
> 
> >    b  b  a
> 
> >
> 
> > and I'd like to turn this into a Python array:
> 
> 
> 
> You mean a Python list. The datatype Python calls an `array` is very
> 
> different and relatively uncommonly used.
> 
> Although, confusingly, Python's lists are implemented using C arrays
> 
> rather than linked lists.

The list in python is a list of valid python objects.
For the number crunching part, please use  arrays in numarray and scipy. 

> 
> >   1 2 1
> 
> >   2 2 1
> 
> >
> 
> > so 1 replaces a, and 2 replaces b. Here's the code I have so far:
> 
> >
> 
> >>>> L=['a b a\n','b b a\n']
> 
> <snip>
> 
> >>>> seq
> 
> > '1 2 1\n 2 2 1\n'
> 
> >
> 
> > My question is how can I turn "seq" into a python array?
> 
> 
> 
> I'd say you're asking the wrong question. The better question is "Why
> 
> wasn't the result a list in the first place?". Many transformations
> 
> are cumbersome to express over just strings, which is why the first
> 
> job of most programs is to parse their input into a more convenient
> 
> structure that is suited to their main task(s).
> 
> 
> 
> This (along with some other improvements) leads to a better, somewhat
> 
> different program/algorithm:
> 
> 
> 
> letter2number = {'a': 1, 'b': 2}
> 
> with open("path/to/file.txt", "r") as f:
> 
>     result = [[letter2number[letter] for letter in
> 
> line.strip().split()] for line in f]
> 
> 
> 
> If it's safe to assume that the correspondence between the letters and
> 
> numbers isn't completely arbitrary, some further improvements are also
> 
> possible.
> 
> 
> 
> Some relevant docs:
> 
> http://docs.python.org/library/stdtypes.html#string-methods
> 
> http://docs.python.org/tutorial/datastructures.html#list-comprehensions
> 
> 
> 
> Cheers,
> 
> Chris
> 
> 
> 
> P.S.: I'm guessing you obtained `L` from file.readlines() or similar;
> 
> it is worth noting for future reference that the readlines() method is
> 
> considered somewhat deprecated.