How can I print literal curly-brace characters in a string and also use .format on it?

Question

x = " \{ Hello \} {0} " print(x.format(42)) 

gives me : Key Error: Hello\\

I want to print the output: {Hello} 42

Answer 1

You need to double the {{ and }}:

>>> x = " {{ Hello }} {0} " >>> print(x.format(42)) ' { Hello } 42 ' 

Here's the relevant part of the Python documentation for format string syntax:

Format strings contain “replacement fields” surrounded by curly braces {}. Anything that is not contained in braces is considered literal text, which is copied unchanged to the output. If you need to include a brace character in the literal text, it can be escaped by doubling: {{ and }}.

Answer 2

Python 3.6+ (2017)

In the recent versions of Python one would use f-strings (see also PEP498).

With f-strings one should use double {{ or }}

n = 42   print(f" {{Hello}} {n} ") 

produces the desired

 {Hello} 42 

If you need to resolve an expression in the brackets instead of using literal text you'll need three sets of brackets:

hello = "HELLO" print(f"{{{hello.lower()}}}") 

produces

{hello}