F-strings provide a convenient way to format strings in Python. However, when working with dynamic templates or files, the need arises to postpone or defer the evaluation of f-strings. This poses a challenge as static strings with formatting tags cannot be directly interpreted by the interpreter.
A robust solution to this problem involves using a custom function that evaluates a string as an f-string. The following function serves this purpose:
<code class="python">def fstr(template): return eval(f'f"""{template}"""')</code>
With the fstr function, you can postpone f-string evaluation as follows:
<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>
Notice that the fstr function correctly evaluates expressions within the string, such as name.upper() * 2:
<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>
This approach provides a concise and convenient way to handle f-string evaluation when necessary, allowing for dynamic string formatting within your codebase.
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