[Tutor] bash heredoc and python

[David Lowry-Duda]

I like to use python as a simple commandline calculator. I only just 
learned that it's possible to do something like the following in bash

```
$ python <<EOF
import math
print('multiple lines')
print(math.pi)
```

and python will happily run this. I had thought this wouldn't work, and 
that python would instead complain that there was no file with some 
amalgamated name.

I discovered this by an accident, but googling shows of course that this 
isn't new or anything. I would have expected this to run with "python - 
<<EOF" instead of "python <<EOF", as the `-` indicates to read from 
stdin.

So I opened up the python manpage to see about this, and saw nothing 
there (not even about what `-` is supposed to mean!). Then I went to

https://docs.python.org/3/using/cmdline.html#command-line

to see if I could learn more, and I don't see much there either. There 
is a somewhat cryptic remark: "In non-interactive mode, the entire input 
is parsed before it is executed."

I guess python does something like: check to see if args were given, if 
not then check for standard input and then run it noninteractively? Do 
you think this is an intended behavior, or is this merely an 
undocumented implementation detail?

- DLD