Python IF THEN chain equivalence

Diez B. Roggisch deets at nospam.web.de
Thu Nov 13 23:11:12 CET 2008


jzakiya schrieb:
> I'm translating a program in Python that has this IF Then chain
> 
> 
> IF  x1 < limit:   --- do a ---
>     IF  x2 < limit:  --- do b ---
>         IF x3 < limit:  --- do c ---
>                        .-----
>                         ------
>                     IF  x10 < limt: --- do j ---
>                     THEN
>                  THEN
>               -----
>           THEN
>      THEN
> THEN
> 
> In other words, as long as    'xi' is less than 'limit' keep going
> down the chain, and when 'xi' isn't less than 'limit' jump to end of
> chain a continue.
> 
> Is this the equivalence in Python?
> 
>  IF  x1 < limit:
>         --- do a  ---
>  elif x2 < limit:
>         --- do b ---
>  ----
>  ----
>  elif x10 < limit:
>        --- do j ---

Of course not. After "do a", it would stop.

You need to use

if x1 < limit:
    do a
    if x2 < limit:
       do b
       ...


Alternatively, and depending on the nature of "do X", you can do

for x, todo in ((x1, do_a), (x2, do_b), ...):
     if x < limit:
        todo()
     else:
        break

This implies though that the "dos" are pure functions without (variable) 
arguments.

Diez



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