Python String Format Explanation

Question

I saw this in a code,

print('Job: {!r}, {!s}'.format(5,3))

and the answer is

Job: 5, 3

how does {!r} evaluate? Does it have any special meaning there?

Answer 1

!r calls repr() on the value before interpolating.

For integers, the str(), default format() and repr() output doesn't differ. For other types, such as strings, the difference is more visible:

>>> print('Repr of a string: {!r}'.format("She said: 'Hello, world!'"))
Repr of a string: "She said: 'Hello, world!'"

Note that quotes were included.

See the Format String Syntax; the character after ! specifies the conversion applied to the value. The default is no conversion, but you can use either !r or !s to convert a value to its repr() representation or str() string output, respectively.

You'd usually use conversion when either dealing with a type that doesn't specify an explicit __format__() method (such as bytes), when explicitly formatting to the repr() output (very helpful for debug output), or when you have to handle a mix of types.