This is a logical statement that is technically true while not matching real-world experience. Scripting as a type of programming is different from application development programming, and scripting needs differences in features and interface to be convenient and comfortable.

> There is nothing in the problem domain that requires the posix string-substitution problems.

What do you mean? Environment variables and command line execution both separately lead to string substitutions. The fish shell uses string substitutions.

You emphasized ‘requires’ which again might make your statement technically true while still missing the experiential forest for the logical trees. You can use x86 assembly for your shell if you want, there’s nothing that “requires” posix. The reason string substitutions exist is because they’re useful and convenient; the alternatives are verbose and klunky.

Whitespace sensitivity is horrendous (can’t autoformat, no multi-line lambdas, bonkers inline list comprehensions) but here we are.

Pray tell which one of the myriad is the true one?

And do not worry, no one would be rash enough to bring in external dependencies it is just too darn inconvenient.

I should probably drink my coffee before posting, be less grumpy.

Python is a full-on programming language. Its REPL is a REPL for that language. Interacting with the OS and filesystem is a niche, tucked away in a corner of the language.

It has has none of the ergonomic affordances needed to be the user interface for interacting with files and processes.

Here are some simple commands:

    ls
    cd foo
    ls
    rm bar
    cd ../baz
    rm bar
    echo >readme.txt baz directory
    curl -s http://example.com >download

    python
    >>> ls
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    NameError: name 'ls' is not defined
    >>> import system
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    ModuleNotFoundError: No module named 'system'
    >>> import os
    >>> os.dir.list()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    AttributeError: module 'os' has no attribute 'dir'
    >>> help(os)

    >>> os.listdir()
    ['foo', 'bar', 'baz']
    >>> cd foo
      File "<stdin>", line 1
        cd foo
           ^
    SyntaxError: invalid syntax
    >>> chdir("foo")
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    NameError: name 'chdir' is not defined
    >>> os.chdir("foo")
    >>> os.listdir()
    ['bar']
    >>> os.delete("bar")
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    AttributeError: module 'os' has no attribute 'delete'
    >>> os.remove("bar")
    >>> os.chdir("../baz")
    >>> os.remove("bar")
    >>> f = open("readme.txt", "w")
    >>> f.write("baz directory")
    13
    >>> f.close()
    >>> import process
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    ModuleNotFoundError: No module named 'process'
    >>> import subprocess
    >>> subprocess.run("curl", "-s", "http://example.com/")
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/usr/lib/python3.9/subprocess.py", line 505, in run
        with Popen(*popenargs, **kwargs) as process:
      File "/usr/lib/python3.9/subprocess.py", line 778, in __init__
        raise TypeError("bufsize must be an integer")
    TypeError: bufsize must be an integer
    >>> subprocess.run(["curl", "-s", "http://example.com/"])
    ...
    CompletedProcess(args=['curl', '-s', 'http://example.com/'], returncode=0)
    >>> subprocess.run(args=["curl", "-s", "http://example.com/"], capture_output=True)
    CompletedProcess(args=['curl', '-s', 'http://example.com/'], returncode=0, stdout=b'...\n', stderr=b'')
    >>> p = subprocess.run(args=["curl", "-s", "http://example.com/"], capture_output=True)
    >>> fh = open("download", "w")
    >>> fh.write(p.stdout)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    TypeError: write() argument must be str, not bytes
    >>> fh = open("download", "wb")
    >>> fh.write(p.stdout)
    559
    >>> fh.close()