Context locals¶

Want desired context’s locals¶

From a module function, get the locals and return value

When testing and an Exception occurs, the locals are only available in the context of where the error occurred, not necessarily where need to debug.

As you read this, keep in mind

To understand our motivation, how badly we want to see those locals, background on those locals:

param_a – Satoshi Nakamoto’s private key to the genesis block

param_b – the passphrase to that private key

^^ is exactly how it feels when don’t have access to those locals and then suddenly do!

—Betty White <– everything is attributed to her

Limited to:

module function; not a: class method, Generator, Iterator, or Iterable
function must end in a single return statement; not yield, yield from, or raise

And wait! There’s more¶

In return, value can be: normal or tuple (packed values)

Wow!

Great!

Yea!

One return value example¶

Example function found in logging_strict.tech_niques.context_locals. Lets pretend this is the module level function would like to see the locals

def _func(param_a: str, param_b: Optional[int] = 10) -> str:
    param_a = f"Hey {param_a}"  # Local only
    param_b += 20  # Local only
    return "bar"

So there are two locals we’d really really like to see:

param_a
param_b

Returns "bar"

from logging_strict.tech_niques.context_locals import get_locals_dynamic, _func


def main():
    # If in same script file try, f"{__name__}._func"
    func_path = f"logging_strict.tech_niques.context_locals._func"

    args = ("A",)
    kwargs = {}
    t_ret = get_locals_dynamic(_func, *args, **kwargs)
    ret, d_locals = t_ret
    assert ret == "bar"
    assert "param_a" in d_locals.keys()
    assert "param_b" in d_locals.keys()
    print(d_locals)


main()

{'full_name': '_func', 'param_a': 'Hey A', 'param_b': 30}

Woooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo- oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooah!

Note

pretty print is your friend

For better readability, pprint.pprint() is better than print()

Note

__name__ is also your friend

This technique requires the absolute dotted path to the module function. if in the same (python script) file, use f"{__name__}.myfunc" instead.

Useful knowhow, if the module function is in the same file as a unittest

Caution

Especially applies to JSON

tl;dr;

In a str, preserve escape characters, use raw string, e.g. r”\\n”

“\\n” –> “\n”

Unpreserved, ^^ may happen

Escape characters need to be preserved. JSON str is an example where a raw string would preserve the escaped characters and remain valid JSON.

Context locals¶

Want desired context’s locals¶

And wait! There’s more¶

One return value example¶

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