How to postpone/defer the evaluation of f-strings?

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Here’s a complete “Ideal 2”.

It’s not an f-string—it doesn’t even use f-strings—but it does as requested. Syntax exactly as specified. No security headaches since we are not using eval().

It uses a little class and implements __str__ which is automatically called by print. To escape the limited scope of the class we use the inspect module to hop one frame up and see the variables the caller has access to.

import inspect

class magic_fstring_function:
    def __init__(self, payload):
        self.payload = payload
    def __str__(self):
        vars = inspect.currentframe().f_back.f_globals.copy()
        vars.update(inspect.currentframe().f_back.f_locals)
        return self.payload.format(**vars)

template = "The current name is {name}"

template_a = magic_fstring_function(template)

# use it inside a function to demonstrate it gets the scoping right
def new_scope():
    names = ["foo", "bar"]
    for name in names:
        print(template_a)

new_scope()
# The current name is foo
# The current name is bar

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