while c = f.read(1)

[Antoon Pardon]

Op 2005-08-19, Donn Cave schreef <donn at drizzle.com>:
> Quoth "Greg McIntyre" <greg at puyo.cjb.net>:
>| I have a Python snippet:
>|
>|   f = open("blah.txt", "r")
>|   while True:
>|       c = f.read(1)
>|       if c == '': break # EOF
>|       # ... work on c
>|
>| Is some way to make this code more compact and simple? It's a bit
>| spaghetti.
>
> Actually I'd make it a little less compact -- put the "break"
> on its own line -- but in any case this is fine.  It's a natural
> and ordinary way to express this in Python.
>
> ...
>| But I get a syntax error.
>|
>|     while c = f.read(1):
>|            ^
>| SyntaxError: invalid syntax
>|
>| And read() doesn't work that way anyway because it returns '' on EOF
>| and '' != False. If I try:
>
> This is the part I really wanted to respond to.  Python managed
> without a False for years (and of course without a True), and if
> the introduction of this superfluous boolean type really has led
> to much of this kind of confusion, then it was a bad idea for sure.

IMO the confusion is the result of True and False appearing late.

IMO having python interpret None, '', (), {} and [] as false in
a conditional context goes against the spirit of:

  In the face of ambiguity, refuse the temptation to guess.

> The condition that we're looking at here, and this is often the
> way to look at conditional expressions in Python, is basically
> something vs. nothing.  In this and most IO reads, the return
> value will be something, until at end of file it's nothing.
> Any type of nothing -- '', {}, [], 0, None - will test "false",

But '', {}, [] and () are not nothing. They are empty containers.
And 0 is not nothing either it is a number. Suppose I have
a variable that is either None if I'm not registered and a
registration number if I am. In this case 0 should be treated
as any other number.

Such possibilities, make me shy away from just using 'nothing'
as false and writing out my conditionals more explicitly.

-- 
Antoon Pardon