F-strings provide a new, concise way to format strings in Python 3.6. They allow embedding expressions inside curly braces within a string that starts with f. This allows printing variables directly into a string without needing string formatting or .format() methods. F-strings are faster than older string formatting methods and make multiline strings easier to read by allowing expressions across multiple lines. Documentation on f-strings can be found in the Python docs glossary under "formatted string literal".

1. F-STRINGS
@mariatta

2. F-strings?

3. The new way to format strings
… starting in Python 3.6

4. How?

5. How we format strings before ...
>>> name = “Bart”
>>> print("Hello, %s." % name)
Hello, Bart.

6. More than one argument?
>>> name = “Bart”
>>> age = 10
>>> print("Hello, %s. You’re %s." % name, age)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: not enough arguments for format string

7. More than one argument?
>>> name = “Bart”
>>> age = 10
>>> print("Hello, %s. You’re %s." % (name, age))
Hello, Bart. You’re 10.

8. str.format
>>> name = “Bart”
>>> age = 10
>>> print("Hello, {name}. You’re {age}.".format(name=name,age=age))
Hello, Bart. You’re 10.

9. F-string
>>> name = “Bart”
>>> age = 10
>>> print(f"Hello, {name}. You’re {age}.")
Hello, Bart. You’re 10.

10. Quick recap
"Hello, %s. You’re %s." % (name, age)
"Hello, {name}. You’re {age}.".format(name=name, age=age)
f"Hello, {name}. You’re {age}."

11. Alternate usage
f"Hello, {name}. You’re {age}."
F"Hello, {name}. You’re {age}."

12. Calling a function
>>> def to_uppercase(input):
... return input.upper()
...
>>> name = “bart simpson”
>>> print(f"Hi {to_uppercase(name)}!")
Hi BART SIMPSON!

13. Multiline strings?
>>> name = “Bart”
>>> prize = 50
>>> deadline = “April 30, 2017”
>>> message = (f"Dear {name},"
... "Here is a chance to win {prize}$"
... "Simply make a purchase before {deadline}")

14. >>> message = (f"Dear {name},"
... f"Here is a chance to win {prize}$"
... f"Simply make a purchase before {deadline}")

15. F-strings

16. ... faster than str.format

17. ... require Python 3.6
Download at https://www.python.org
v3.6.1 is recommended

18. … documentation?

19. docs.python.org > glossary > f-string
“formatted string literal”

20. Thank you!
@mariatta | mariatta@python.org
File issues at https://bugs.python.org
(aka the b.p.o)