In Python's string.Template, which method raises an error if a placeholder in the template has no corresponding value?

In Python's string.Template, which method raises an error if a placeholder in the template has no corresponding value?

• A. Substitute
• B. Safe_substitute
• C. Format
• D. Render

Answer: (A)

When a template has placeholders that must be filled, you want to know what happens if one is missing a value. In Python’s string.Template, there are two ways to substitute: substitute and safe_substitute. The method that raises an error when a placeholder has no corresponding value is substitute. If you try to fill a template like "Hello, $name" with a mapping that doesn’t provide name, substitute raises a KeyError, signaling that a required value is missing. This strict behavior helps catch mistakes where data didn’t get supplied or a placeholder was misnamed. Safe_substitute, by contrast, would not raise an error in that case; it would leave the placeholder unresolved or only substitute the provided values, which can hide missing data. The other options aren’t part of string.Template’s substitution methods—format refers to a different formatting approach, and render isn’t a method in this context.

When a template has placeholders that must be filled, you want to know what happens if one is missing a value. In Python’s string.Template, there are two ways to substitute: substitute and safe_substitute. The method that raises an error when a placeholder has no corresponding value is substitute. If you try to fill a template like "Hello, $name" with a mapping that doesn’t provide name, substitute raises a KeyError, signaling that a required value is missing. This strict behavior helps catch mistakes where data didn’t get supplied or a placeholder was misnamed. Safe_substitute, by contrast, would not raise an error in that case; it would leave the placeholder unresolved or only substitute the provided values, which can hide missing data. The other options aren’t part of string.Template’s substitution methods—format refers to a different formatting approach, and render isn’t a method in this context.