Unmatched python ошибка

To fix the SyntaxError: f-string: unmatched ‘(‘ in Python, you need to pay attention to use single or double quotes in f-string. You can change it or not use it. Please read the following article for details. 

New built-in string formatting method from Python 3.6 in the following syntax:

f''a{value:pattern}b''

Parameters:

• f character: use the string f to format the string.
• a,b: characters to format.
• {value:pattern}: string elements need to be formatted.
• pattern: string format.

In simple terms, we format a string in Python by writing the letter f or F in front of the string and then assigning a replacement value to the replacement field. We then transform the replacement value assigned to match the format in the replace field and complete the process.

The SyntaxError: f-string: unmatched ‘(‘ in Python happens because you use unreasonable single or double quotes in f-string.

Example: 

testStr = 'visit learnshareit website'

# Put variable name with the string in double quotes in f-string for formatting
newStr = f"{(testStr + "hello")}"
print(newStr)

Output:

  File "code.py", line 4
    newStr = f"{(testStr + "hello")}"
                            ^
SyntaxError: invalid syntax

How to solve this error?

Change the quotes

The simplest way is to change the quotes. If your f-string contains double quotes, put the string inside it with single quotes.

Example:

testStr = 'visit learnshareit website'

# Use single quotes for strings in f-string when f-string contains double quotes
newStr = f"{(testStr + ' hello')}"
print(newStr)

Output:

visit learnshareit website hello

Similarly, we will do the opposite if the f-string carries single quotes. The string in it must carry double quotes.

Example:

testStr = 'visit learnshareit website'

# f-string contains single quotes. The string must contain double quotes
newStr = f'{(testStr + " hello")}'
print(newStr)

Output:

visit learnshareit website hello

Do not use single or double quotes

If the problem is with quotes confusing you, limit their use inside the f-string.

Example:

• I want to concatenate two strings instead of using quotes inside the f-string. Then I declare 2 variables containing two strings and use the addition operator to concatenate two strings inside f-string so that will avoid SyntaxError: f- string: unmatched ‘(‘.

testStr = 'visit learnshareit website'
secondStr = '!!!'

newStr = f'{ testStr + secondStr }'
print(newStr)

Output:

visit learnshareit website!!!

Summary

The SyntaxError: f-string: unmatched ‘(‘ in Python has been resolved. You can use one of two methods above for this problem. If there are better ways, please leave a comment. We appreciate this. Thank you for reading!

Maybe you are interested:

• How To Resolve SyntaxError: ‘Break’ Outside Loop In Python
• How To Resolve SyntaxError: f-string: Empty Expression Not Allowed In Python
• How To Resolve SyntaxError: F-string Expression Part Cannot Include A Backslash In Python

The f strings are commonly used for better formatting Python strings. Also referred to as Formatted string literals, f strings are widely used for formatting. However, one may encounter an error that is majorly syntactical while working on f strings. Review this blog to learn more about the ‘f string unmatched’ error.

What are f strings in Python?

Python has a f string type, which is a formatted string literal. A formatted string literal is just what it sounds like. It’s a string that you can format using special characters, such as the percent sign (%) and the ampersand (&), to create formatting rules.

These strings contain both the actual text and formatting information, such as fonts or so that your program can render correctly and then print out by the computer. This is useful for things like printing out data from databases or from other programs, so you can see how it will look when it’s outputted.

How do format strings/plain text?

You can utilize format text in two ways: literals or formatting expressions.

A literal is a text inside your program; an expression is any piece of code that produces some value or action. In this case, we’ll focus on formatting expressions since they’re more common than literals (but both will work).

To format text using Python, you must use either the str() function or the built-in repr() function. The str() function returns a formatted string object. This object is also known as FPM. It contains all of the information about how your text should be displayed when printed out.

Why you got the f string unmatched error?

This might have happened when the quotes used with f strings don’t match. For example, if you have used double quotes with double quotes in your string or single quotes with single quotes, this error is likely to occur.

Resolution of error

Normally, the f string should have either double or single quotes along with the other quotes type. For example, it can be either double quotes with a single quote or a single with a double quote. In case you mix them, it will result in f string unmatched error.

f"hello ' correct"
#or
f'hello " correct'

On the other hand, if it is a double with a double quote or a single quote with a single quote, you will get the error. Hence, check for the quotes.

f"hello " wrong "
#or
f'hello ' wrong'
# will give error.

Hence, wrapping the text in the opposite quotes type will make the code error-free. Let us observe another example to get a better view of the resolution of the error.

game = 'chess'
print(f"GAME: {game.replace('chess', 'ludo')}")

They are easier to read and use. Infact, they’re similar to printf() functions in other languages, but they come with many advantages say they can be used as a replacement for print() in your code. Also, they can be easily parsed by the Python interpreter.

Besides this, a few extra features including custom format specifiers and inserting newlines into output are also available with f strings. So they are of great use to anyone who’s coding in Python.

f strings with triple quotes

In case you have used double and single quotes, you may use triple quotes.

game = 'chess'
print(f"""games: {game.replace("chess", "ludo")}""")

You may check this article too: How to Remove Quotes From a String in Python(Opens in a new browser tab)

f strings with correct braces

Wherever you require the string to be formatted, use a curly brace instead of any other type of braces.

lang = 'python'
print(f'language: {lang}')  

And the output will be:

f strings with square brackets

Square brackets work when we are accessing dictionary items using f strings.

website = {'site': 'pythonpool'}
print(f"site_a: {website['site']}")

f strings with backslash

Python doesn’t allow a user to use backslash directly with the format string. So in case you wish to apply backslash in a statement, store that backslash in a variable and use f string formatting with the variable.

Input = ord('\n')
print(f"newline: {Input}")
#this backslash works now as f string #formatting is used with the variable only.

f strings with decimal values

You may try using f string formatting with decimal notation values. You need to specify the precision value also. It means how many digits you want after the decimal. It uses this syntax:

f'{value:{width}.{precision}'

For example, look at this code:

No = 550.9999
print(f'{No:.2f}')
#will result in '550.99'

Advantages of using f strings over other formatting options

Python’s f strings are a shorthand for calling the format() function. They’re useful for writing short functions that wrap up formatting in one line of code. The advantage of f strings is that they use the same syntax as other methods and functions, which means you can take advantage of all the built-in tools in the language.

In addition to being shorter than your regular function calls, they also have a few other advantages. They don’t require any arguments (unlike format()). They don’t require any whitespace after the method name (unlike format()) and they work on both Python 2 and 3 (unlike format()).

f strings or format strings?

F strings can be used in place of format strings where the string representation isn’t important. The main difference between them is that f string supports unicode strings whereas format function only works with text.

Format strings require additional logic to get text out of a variable or object, while f string only requires an integer index (as long as the variable or object has an ordinal).

This means that you can use unicode characters in your f strings and they’ll work just like normal strings. This can be useful when working with internationalized data or sending text messages over the internet.

You should also consider using f string if you want to add some flexibility to your string formatting, since it allows you to add more options for how your string will display.You can use the + operator to combine two or more formatting options together into one string, which makes writing complex formatting logic easier than using the format function alone.

FAQs

Conclusion

This article resolved the ‘f string unmatched error’ and discussed ways to prevent it. In this tutorial, we also learned how to use Python’s f string type using the str.format() function.

Created on 2021-09-02 14:55 by Greg Kuhn, last changed 2022-04-11 14:59 by admin. This issue is now closed.

Messages (9)
msg400920 — (view)	Author: Greg Kuhn (Greg Kuhn)	Date: 2021-09-02 14:55
Hi All, Is the below a bug? Shouldn't the interpreter be complaining about a curly brace? $ python Python 3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:43:08) [MSC v.1926 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> num = 10 >>> f'[{num]' File "<stdin>", line 1 SyntaxError: f-string: unmatched ']' >>>
msg400925 — (view)	Author: Eric V. Smith (eric.smith) *	Date: 2021-09-02 15:29
I think the error is short for "I found a ']' without a matching '['".
msg400930 — (view)	Author: Greg Kuhn (Greg Kuhn)	Date: 2021-09-02 15:45
But doesn't the square bracket have no relevance here? It's not within a curly bracketed string so shouldn't be treated specially. I would have expected the error to be: SyntaxError: f-string: unmatched '}'. Unless I need to go back and reread pep498...
msg400942 — (view)	Author: Eric V. Smith (eric.smith) *	Date: 2021-09-02 17:17
I think it's basically this error: >>> num] File "<stdin>", line 1 num] ^ SyntaxError: unmatched ']' Although I'd have to look at it more to see why that's the error it chose to display, instead of the curly brace.
msg401029 — (view)	Author: Terry J. Reedy (terry.reedy) *	Date: 2021-09-04 02:06
The behavior remains the same in 3.11 ('main' branch). New PEG parser parses this the same. (Pablo, if there is a mistake below, please correct.) Normally, the parser copies code chars between quotes, with or without '\' interpretation, into a string object. When the 'f' prefix is given, the string gets divided into substrings and replacement fields. The code part of each replacement field is separately parsed. There are two options: 1. parse the field code while looking for an endcode marker; 2. look ahead for an endcode marker and then parse the code. The current behavior is consistent with opotion 1 and the python policy of reporting the first error found and exiting, rather than trying to resynchronize to try to find more errors.
msg401034 — (view)	Author: Eric V. Smith (eric.smith) *	Date: 2021-09-04 02:58
I don't think it really makes a difference, but here's some background: For f-strings, the parser itself does not break apart the f-string into (<text>, <expression>) parts. There's a custom parser (at https://github.com/python/cpython/blob/0b58e863df9970b290a4de90c67f9ac30c443817/Parser/string_parser.c#L837) which does that. Then the normal parser is used to parse the expression portion. I think the error shown here is not in the expression parser, but in the fstring parser in fstring_find_expr(), at https://github.com/python/cpython/blob/0b58e863df9970b290a4de90c67f9ac30c443817/Parser/string_parser.c#L665 As Terry says, it's not incorrect to print the error show in this bug report. To further diverge: There's been talk about using the normal parser to pull apart the entire f-string, instead of using the two-pass version I mention above. But we've never gotten past just talking about it. There are pros and cons for doing it with the normal parser, but that's a discussion for a different forum.
msg401042 — (view)	Author: Pablo Galindo Salgado (pablogsal) *	Date: 2021-09-04 12:29
> But we've never gotten past just talking about it Stay tuned! :) https://github.com/we-like-parsers/cpython/tree/fstring-grammar
msg401046 — (view)	Author: Terry J. Reedy (terry.reedy) *	Date: 2021-09-04 16:38
Thank you Eric. I can see now that the actual process is a somewhat complicated mix of the simple options 1 and 2 I imagined above. It is like option 2, except that everything between '{' and '}' is partially parsed enough to create a format object. This is required to ignore quoted braces >>> f'{"}"' SyntaxError: f-string: expecting '}' and detect valid '!' and ':' markers. In that partial parsing, unmatched fences are detected and reported, while other syntax errors are not. If my option 1 above were true, the first example below would instead report the 'a a' error. >>> f'{a a' SyntaxError: f-string: expecting '}' >>> f'{a a]' SyntaxError: f-string: unmatched ']' >>> f'{a a}' SyntaxError: f-string: invalid syntax. Perhaps you forgot a comma? The second plausibly could, but outside of the f-string context, the error is the same. >>> a a] SyntaxError: unmatched ']' Greg, the fuller answer to your question is that the interpreter is only *required* to report that there is an error and some indication of where. "SyntaxError: invalid syntax" is the default. It may have once been all that was ever reported. A lot of recent effort has gone into adding detail into what is wrong and what the fix might be. But both additions sometimes involve choices that may not meet a particular person's expectation. Another person, expecting linear rather than nested parsing, might look at the first example above and ask whether the interpreter should be complaining about the 'a a' syntax error instead of the following lack of '}' f-string error. And I would not call it a bug if it were to do so in the future.
msg401048 — (view)	Author: Greg Kuhn (Greg Kuhn)	Date: 2021-09-04 17:35
I see, thank you all for the detailed investigation and explanation!! Agreed Terry, anyone who reads the error should be able to parse it themselves and see what the errors is. Pointing the user to the error site is the most important piece.