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Diffstat (limited to 'Doc/howto/functional.rst')
| -rw-r--r-- | Doc/howto/functional.rst | 20 |
1 files changed, 9 insertions, 11 deletions
diff --git a/Doc/howto/functional.rst b/Doc/howto/functional.rst index ebbb229e57..7189c65127 100644 --- a/Doc/howto/functional.rst +++ b/Doc/howto/functional.rst @@ -292,13 +292,14 @@ ordering of the objects in the dictionary. Applying :func:`iter` to a dictionary always loops over the keys, but dictionaries have methods that return other iterators. If you want to iterate over values or key/value pairs, you can explicitly call the -:meth:`~dict.values` or :meth:`~dict.items` methods to get an appropriate iterator. +:meth:`~dict.values` or :meth:`~dict.items` methods to get an appropriate +iterator. The :func:`dict` constructor can accept an iterator that returns a finite stream of ``(key, value)`` tuples: >>> L = [('Italy', 'Rome'), ('France', 'Paris'), ('US', 'Washington DC')] - >>> dict(iter(L)) + >>> dict(iter(L)) #doctest: +SKIP {'Italy': 'Rome', 'US': 'Washington DC', 'France': 'Paris'} Files also support iteration by calling the :meth:`~io.TextIOBase.readline` @@ -478,13 +479,10 @@ Here's a sample usage of the ``generate_ints()`` generator: You could equally write ``for i in generate_ints(5)``, or ``a,b,c = generate_ints(3)``. -Inside a generator function, the ``return`` statement can only be used without a -value, and signals the end of the procession of values; after executing a -``return`` the generator cannot return any further values. ``return`` with a -value, such as ``return 5``, is a syntax error inside a generator function. The -end of the generator's results can also be indicated by raising -:exc:`StopIteration` manually, or by just letting the flow of execution fall off -the bottom of the function. +Inside a generator function, ``return value`` is semantically equivalent to +``raise StopIteration(value)``. If no value is returned or the bottom of the +function is reached, the procession of values ends and the generator cannot +return any further values. You could achieve the effect of generators manually by writing your own class and storing all the local variables of the generator as instance variables. For @@ -689,8 +687,8 @@ constructed list's :meth:`~list.sort` method. :: The :func:`any(iter) <any>` and :func:`all(iter) <all>` built-ins look at the -truth values of an iterable's contents. :func:`any` returns True if any element -in the iterable is a true value, and :func:`all` returns True if all of the +truth values of an iterable's contents. :func:`any` returns ``True`` if any element +in the iterable is a true value, and :func:`all` returns ``True`` if all of the elements are true values: >>> any([0,1,0]) |