Return and yield in the same function

by

Yes, it’ still a generator. The return is (almost) equivalent to raising StopIteration.

PEP 255 spells it out:

Specification: Return

A generator function can also contain return statements of the form:

"return"

Note that an expression_list is not allowed on return statements in
the body of a generator (although, of course, they may appear in the
bodies of non-generator functions nested within the generator).

When a return statement is encountered, control proceeds as in any
function return, executing the appropriate finally clauses (if any
exist). Then a StopIteration exception is raised, signalling that the
iterator is exhausted. A StopIteration exception is also raised if
control flows off the end of the generator without an explict return.

Note that return means “I’m done, and have nothing interesting to
return”, for both generator functions and non-generator functions.

Note that return isn’t always equivalent to raising StopIteration:
the difference lies in how enclosing try/except constructs are
treated. For example,

>>> def f1():
...     try:
...         return
...     except:
...        yield 1
>>> print list(f1())
[]

because, as in any function, return simply exits, but

>>> def f2():
...     try:
...         raise StopIteration
...     except:
...         yield 42
>>> print list(f2())
[42]

because StopIteration is captured by a bare “except”, as is any
exception.

More Related Contents:

  1. In practice, what are the main uses for the “yield from” syntax in Python 3.3?
  2. Resetting generator object in Python
  3. yield in list comprehensions and generator expressions
  4. Converting “yield from” statement to Python 2.7 code
  5. Why is this python generator returning the same value everytime?
  6. Recursion using yield
  7. How to use ‘yield’ inside async function?
  8. What does the “yield” keyword do in Python?
  9. Is there a way to efficiently yield every file in a directory containing millions of files?
  10. How do I use raw_input in Python 3
  11. Lost connection to MySQL server during query
  12. Differences between numpy.random and random.random in Python
  13. Python-Requests close http connection
  14. re.sub erroring with “Expected string or bytes-like object”
  15. Use scikit-learn to classify into multiple categories
  16. Assigning values to variables in a list using a loop
  17. What is python’s site-packages directory?
  18. Pandas compare next row
  19. Why subprocess.Popen doesn’t work when args is sequence?
  20. Matplotlib: display plot on a remote machine
  21. Python generator expression parentheses oddity
  22. How to get all combination of n binary value? [duplicate]
  23. Convert a columns of string to list in pandas
  24. Object becomes None when using a context manager
  25. How can I get text of an element in Selenium WebDriver, without including child element text?
  26. Pygame: problems with shooting in Space Invaders
  27. How to solve import error for pandas?
  28. Computing Standard Deviation in a stream
  29. How to adapt or resize a rectangle inside an object without including (or with a few numbers) of background pixels?
  30. PySide2 QMainWindow loaded from ui file not triggering window events

Leave a Comment