[Tutor] String switch

[Dave Angel]

On 10/08/2011 03:03 PM, Christopher King wrote:
> Okay, here's what I what to do
> *--Target.py--*
> print "Hello World"
> *--Target.py Output--*
> *Hello World*
> *--Main.py--*
> target=open("target.py", "r")
> old=target.read()
> target.close()
> target=open("target.py", "w")
> target.write('''
> Str.__repr__ = Str.__repr__.swapcase()'''+old)
> target.close()
> *--Modified Target.py--*
> Str.__repr__ = Str.__repr__.swapcase()
> print "Hello World"
> *--Modified Target.py Output--*
> *hELLO wORLD*
>
> The only problem is I don't think that "Str.__repr__ =
> Str.__repr__.swapcase()" works. What should I use in its place to make the
> above a reality.
>
That certainly won't work in Python 2.x, since Str isn't a defined 
symbol.  In any case, I can't see what you intended it to do, since 
__repr__ isn't called anywhere in that code.

What are your constraints?  Which Python version?  Are the only 
allowable changes a prefix to the code in the input file?

What strings do you want modified, only those inside literals, or those 
that are generated by the program?  For example, if the program says
       x = raw_input("What's your name"); print x

do you want that prompt string swapcased as well?  What about the name 
the person types in?

How about a program like
       z = 3.14
        print z.hex()
Do you want the output changed from 0x1.91eb851eb851fp+1
to  0X1.91EB851EB851FP+1   ?

Do you only want things swapped that are printed with "print", or do you 
want anything that goes to stdout?  What about things that are written 
to file?  What about things that are written to a file, but that file 
happens to be stdout ?  Or vice versa?

There are lots of other possible questions, but perhaps that's enough to 
convince you that you haven't begun to specify what you want.

-- 

DaveA