[Python-ideas] AMEND PEP-8 TO DISCOURAGE ALL CAPS

[Cameron Simpson]

On 29Jan2019 15:44, Jamesie Pic <jpic at yourlabs.org> wrote:
>On Fri, Jan 4, 2019 at 10:07 PM Bernardo Sulzbach
><bernardo at bernardosulzbach.com> wrote:
>> I'd suggest violating PEP-8 instead of trying to change it.
>
>TBH even my bash global environment variables tend to become more and
>more lowercase ...

If you mean _exported_ variables, then this is actually a really bad 
idea.

The shell (sh, bash, ksh etc) makes no enforcement about naming for 
exported vs unexported variables. And the exported namespace ($PATH etc) 
is totally open ended, because any programme might expect arbitrary 
optional exported names for easy tuning of defaults.

So, you think, since I only use variables I intend and only export 
variables I plan to, I can do what I like. Example script:

  a=1
  b=2
  export b

So $b is now exported to subcommands, but not $a.

However: the "exported set" is initially the environment you inherit.  
Which means:

Any variable that _arrives_ in the environment is _already_ in the 
exported set. So, another script:

  a=1
  b=2
  # not exporting either

If that gets called from the environment where you'd exported $b (eg 
from the first script, which could easily be your ~/.profile or 
~/.bashrc), then $b gets _modified_ and _exported_ to subcommands, even 
though you hadn't asked. Because it came in initially from the 
environment.

This means that you don't directly control what is local to the script 
and what is exported (and thus can affect other scripts).

The _only_ way to maintain sanity is the existing convention: local 
script variables use lowercase names and exported variables use 
UPPERCASE names. With that in hand, and cooperation from everyone else, 
you have predictable and reliable behaviour. And you have a nice visual 
distinction in your code because you know immediately (by convention) 
whether a variable is exported or not.

By exporting lowercase variables you violate this convention, and make 
your script environment unsafe for others to use.

Do many many example scripts on the web do the reverse: using UPPERCASE 
names for local script variables? Yes they do, and they do a disservice 
to everyone.

Cheers,
Cameron Simpson <cs at cskk.id.au>