use-f-string¶

Collection: fixit-extra Autofix: Yes Python: Any

Prefer f-strings over percent formatting and str.format calls.

Message¶

Do not use printf style formatting or .format(). Use f-string instead to be more readable and efficient.

Setting	Description	Type	Default
simple_expression_max_length	Maximum expression length to autofix inline in an f-string.	int	30

somebody='you'; f"Hey, {somebody}."

"hey"

"hey" + "there"

b"a type %s" % var

u"plain unicode string"

"Hey, {somebody}.".format(somebody="you")

"%s" % "hi"

Suggested fix

f"{'hi'!s}"

"a name: %s" % name

Suggested fix

f"a name: {name!s}"

u"%s" % name

Suggested fix

f"{name!s}"

"an attribute %s ." % obj.attr

Suggested fix

f"an attribute {obj.attr!s} ."

r"raw string value=%s" % val

Suggested fix

fr"raw string value={val!s}"

"{%s}" % val

Suggested fix

f"{{{val!s}}}"

"{%s" % val

Suggested fix

f"{{{val!s}"

"The type of var: %s" % type(var)

Suggested fix

f"The type of var: {type(var)!s}"

"%s" % obj.this_is_a_very_long_expression(parameter)["a_very_long_key"]

Options

simple_expression_max_length = 100

"%s" % abcdefghijklmnopqrstuvwxyz1234567890

Suggested fix

f"{abcdefghijklmnopqrstuvwxyz1234567890!s}"

"type of var: %s, value of var: %s" % (type(var), var)

Suggested fix

f"type of var: {type(var)!s}, value of var: {var!s}"

'%s" double quote is used' % var

Suggested fix

f'{var!s}" double quote is used'

"var1: %s, var2: %s, var3: %s, var4: %s" % (class_object.attribute, dict_lookup["some_key"], some_module.some_function(), var4)

Suggested fix

f"var1: {class_object.attribute!s}, var2: {dict_lookup['some_key']!s}, var3: {some_module.some_function()!s}, var4: {var4!s}"

"a list: %s" % " ".join(var)

Suggested fix

f"a list: {' '.join(var)!s}"

"%s" % (first, second)