How to Resolve f-string Syntax Errors in Python: unmatched '(', expecting '}'

f-strings (formatted string literals) in Python provide a concise way to embed expressions inside string literals. However, incorrect syntax within an f-string can lead to errors like SyntaxError: f-string: unmatched '(' or SyntaxError: f-string: expecting '}'.

This guide explains these errors and how to fix them.

Understanding f-string Syntax

f-strings are string literals prefixed with an f or F. They can contain expressions enclosed in curly braces {}. These expressions are evaluated at runtime, and their results are inserted into the string.

name = "Anna"
age = 23
print(f"My name is {name} and I am {age} years old.")  # Valid f-string

"SyntaxError: f-string: unmatched '('"

This error means you have an opening parenthesis ( within an f-string's expression that is not correctly closed with a matching ). There are two main causes:

Mismatched Quotes

The most common cause is using the same type of quote inside the expression as you used to delimit the f-string itself:

name = 'Anna'

• The outer f-string uses double quotes (").
• The replace() call also uses double quotes, prematurely terminating the f-string.

Solution: Alternate single and double quotes, or use triple quotes:

name = 'Anna'

print(f'employee: {name.replace("Anna", "David")}')  # Output: employee: David

print(f"employee: {name.replace('Anna', 'David')}")  # Output: employee: David

print(f"""employee's name: {name.replace("Anna", "David")}""") # Output: employee's name: David

Unclosed Parentheses within Expressions

If you have any function calls or expressions with parentheses inside the f-string's curly braces, make sure they are correctly closed:

name = 'Tom Nolan'
my_str = f'employee: {name}'
print(my_str)

"SyntaxError: f-string: expecting '}'"

This error indicates a problem with the curly braces {} within your f-string.

Missing Closing Brace

The most common cause is simply forgetting to close a curly brace:

employees = ['tutorial', 'reference', 'com']


my_str = f'Employees list: \n{", ".join(employees)}'
print(my_str)

Output:

Employees list:
tutorial, reference, com

• Carefully check that every opening brace { has a corresponding closing brace }.

Incorrect Quotes within Expressions

Similar to unmatched parentheses, incorrect quote usage within the expression can also cause the error.

emp = {'name': 'Tom Nolan'}
my_str = f'employee: {emp["name"]}'
print(my_str) # Output: employee: Tom Nolan

Conclusion

The SyntaxError: f-string: unmatched '(' and SyntaxError: f-string: expecting '}' errors in Python are caused by incorrect syntax within f-strings. These errors are usually easy to fix once you understand the rules:

• Alternate quotes: Use single quotes around the f-string if your expression contains double quotes, and vice-versa.
• Triple quotes: Use triple quotes (""" or ''') if your expression contains both single and double quotes.
• Matching braces: Every opening curly brace { must have a corresponding closing curly brace }.
• Parentheses: All the parentheses inside the curly braces { and } must be balanced.

By carefully checking your f-string syntax, you can avoid these errors and use the power of f-strings effectively.