Python f-String Expression
Match `{expression}` placeholders inside Python f-strings (or any single-brace template syntax).
Try it in RegexPro →Available in
JavaScript / ECMAScript code
const re = new RegExp("\\{([^{}]+)\\}", "g");
const input = "f\"Hello {name}, you are {age} years old\"";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).
Python (re) code
import re
pattern = re.compile(r"\{([^{}]+)\}")
input_text = "f\"Hello {name}, you are {age} years old\""
for m in pattern.finditer(input_text):
print(m.group(0))Stdlib `re` module — no third-party dependency. Works on Python 3.6+.
Go (RE2) code
package main
import (
"fmt"
"regexp"
)
func main() {
re := regexp.MustCompile(`\{([^{}]+)\}`)
input := `f"Hello {name}, you are {age} years old"`
for _, match := range re.FindAllString(input, -1) {
fmt.Println(match)
}
}Uses `regexp.MustCompile` (panics on bad patterns at startup) and `FindAllString` for all matches.
Pattern
\{([^{}]+)\} (flags: g)Raw source: \{([^{}]+)\}
How it works
Examples
Input
f"Hello {name}, you are {age} years old"Matches
{name}{age}
Input
f"Total: {amount:.2f} USD"Matches
{amount:.2f}
Input
f"escaped {{ not a placeholder }}"No match
—Common use cases
- •Static analysis of f-string usage
- •Linting for unsafe expressions in templates
- •Translating f-strings to .format() during downgrades
- •Generating docs from template files
Related patterns
Triple-Quoted String (Python / TS)
Text ProcessingMatch triple-quoted strings (Python docstrings, TypeScript triple-quote, etc.) including newlines.
JavaScript Template Literal Placeholder
Text ProcessingMatch `${expression}` placeholders inside JavaScript template literals.
Base64 String
Text ProcessingMatch Base64-encoded strings, including proper padding with = and == characters.
Python Import Statement
Text ProcessingMatch Python `import x` and `from x import y` statements, capturing the module and target.