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How to Solve 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
# Output: My name is Anna and I am 23 years old.

"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'

# ⛔️ SyntaxError: f-string: unmatched '('
# print(f"employee: {name.replace("Anna", "David")}")
  • 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'

# ✅ Correct: f-string with single quotes, expression with double quotes
print(f'employee: {name.replace("Anna", "David")}')  # Output: employee: David

# ✅ Correct: f-string with double quotes, expression with single quotes
print(f"employee: {name.replace('Anna', 'David')}")  # Output: employee: David

# ✅ Correct: f-string with triple quotes, expression with any quotes
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:

# ⛔️ SyntaxError: f-string: unmatched '('
#my_str = f'employee: {name)' # Mismatched brackets.

# ✅ Correct
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']

# ⛔️ SyntaxError: f-string: expecting '}'
# my_str = f'Employees list: \n{", ".join(employees)'  # Missing closing }

# ✅ Correct:
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'}
# Incorrect, because the f-string and the dict key both use single quotes:
#my_str = f"employee: {emp['name']}" # Raises error
# ✅ Correct.
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.

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