How to Dynamically Evaluate F-strings?

Evaluating F-strings Dynamically

When utilizing f-strings to create dynamic texts, it can be inconvenient to use the .format(**locals()) method when retrieving templates from external sources. Therefore, a need arises for a mechanism to interpret a string as an f-string.

To address this, a concise function called fstr can be employed:

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

This function enables the direct interpretation of template strings into f-strings, allowing code like this:

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

This code would produce the desired output:

The current name is foo
The current name is bar

Crucially, the fstr function preserves the full capabilities of f-strings, enabling the evaluation of expressions and method calls within the template:

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

Output:

The current name is FOOFOO
The current name is BARBAR

This technique provides a comprehensive solution for dynamically interpreting and evaluating f-strings, simplifying template handling in complex codebases.

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