How Can We Defer the Evaluation of F-Strings Beyond the Immediate Code Context?

Overcoming the Evaluation Quandary in F-Strings

When composing files using template strings, the conciseness of f-strings is highly appealing. However, difficulties emerge when template definitions reside outside the immediate code context. How can we defer the evaluation of f-strings, eliminating the need for the format(**locals()) call?

Enter fstr(), a powerful function that solves this dilemma. Here's how it works:

<code class="python">def fstr(template):
    return eval(f'f&quot;&quot;&quot;{template}&quot;&quot;&quot;')</code>

To use this function, simply call fstr() on the desired template:

<code class="python">template_a = "The current name is {name}"
names = ["foo", "bar"]
for name in names:
    print(fstr(template_a))
# Output:
# The current name is foo
# The current name is bar</code>

Crucially, unlike other proposed solutions, fstr() allows for more complex expressions within the template, including function calls and attribute access:

<code class="python">template_b = "The current name is {name.upper() * 2}"
for name in names:
    print(fstr(template_b))
# Output:
# The current name is FOOFOO
# The current name is BARBAR</code>

With this solution, you can effectively postpone the evaluation of f-strings, preserving their powerful capabilities for succinct and dynamic template handling.

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