best way to ensure './' is at beginning of sys.path?

[Cameron Simpson]

On 04Feb2017 09:19, Wildman <best_lay at yahoo.com> wrote:
>[...]  Personally I don't understand
>the danger in having the dot in the path.  The './'
>only means the current directory.  DOS and Windows
>has searched the current directory since their
>beginning.  Is that also dangerous?

Citing DOS and Windows as prior art doesn't support your "it seems safe" 
argument :-)

When you run a program its behaviour should be predictable. If your execution 
path or python module path includes "." (or some relative-path equivalent) in 
it, the behaviour of the program becomes dependent on where you're standing 
when you invoke it.

Who has not written a shell script called "ls" and left it in their home 
directory, ready for one's friends to visit and run it by accident? Mine kicked 
off a shell script that said "removing files now..." and started reciting 
fictitious "rm" commands. In _their_ home directory. (Since they were invoking 
it, that information is instantly available from $HOME.)

This is why having "." in your path (of whatever flavour), _particularly_ at 
the front (but really in general), is hazardous. At the least your commands 
become subject to misbehaviour through picking up the local (wrong) code; at 
the worst your programs become subverted if somehow malevolent code is sitting 
around somewhere.

Supposing you visit a dev directory with a testing (and _broken_) common module 
or command. Misadventure ensues.

Supposing you're a sysadmin. Nasty!

Supposing you've shunted some malware into a directory for examination? CDing 
_into_ that directoy to do the examination is then _actively dangerous_.

The list goes one.

This is why having "the current directory", of whatever flavour, in your path 
is a bad idea in general.

Cheers,
Cameron Simpson <cs at zip.com.au>