Issue #27204: Fix doctests in Doc/howto

Patch by Jelle Zijlstra.

Doc/howto/functional.rst

@@ -1040,7 +1040,7 @@ If you use :func:`operator.add` with :func:`functools.reduce`, you'll add up all
 elements of the iterable.  This case is so common that there's a special
 built-in called :func:`sum` to compute it:
 
-    >>> import functools
+    >>> import functools, operator
     >>> functools.reduce(operator.add, [1,2,3,4], 0)
     10
     >>> sum([1,2,3,4])

Doc/howto/ipaddress.rst

@@ -1,3 +1,7 @@
+.. testsetup::
+
+   import ipaddress
+
 .. _ipaddress-howto:
 
 ***************************************
@@ -49,11 +53,6 @@ to use the :func:`ipaddress.ip_address` factory function, which automatically
 determines whether to create an IPv4 or IPv6 address based on the passed in
 value:
 
-.. testsetup::
-   >>> import ipaddress
-
-::
-
    >>> ipaddress.ip_address('192.0.2.1')
    IPv4Address('192.0.2.1')
    >>> ipaddress.ip_address('2001:DB8::1')

Doc/howto/sorting.rst

@@ -58,28 +58,28 @@ A common pattern is to sort complex objects using some of the object's indices
 as keys. For example:
 
     >>> student_tuples = [
-        ('john', 'A', 15),
-        ('jane', 'B', 12),
-        ('dave', 'B', 10),
-    ]
+    ...     ('john', 'A', 15),
+    ...     ('jane', 'B', 12),
+    ...     ('dave', 'B', 10),
+    ... ]
     >>> sorted(student_tuples, key=lambda student: student[2])   # sort by age
     [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
 
 The same technique works for objects with named attributes. For example:
 
     >>> class Student:
-            def __init__(self, name, grade, age):
-                self.name = name
-                self.grade = grade
-                self.age = age
-            def __repr__(self):
-                return repr((self.name, self.grade, self.age))
+    ...     def __init__(self, name, grade, age):
+    ...         self.name = name
+    ...         self.grade = grade
+    ...         self.age = age
+    ...     def __repr__(self):
+    ...         return repr((self.name, self.grade, self.age))
 
     >>> student_objects = [
-        Student('john', 'A', 15),
-        Student('jane', 'B', 12),
-        Student('dave', 'B', 10),
-    ]
+    ...     Student('john', 'A', 15),
+    ...     Student('jane', 'B', 12),
+    ...     Student('dave', 'B', 10),
+    ... ]
     >>> sorted(student_objects, key=lambda student: student.age)   # sort by age
     [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
 
@@ -208,15 +208,15 @@ return a negative value for less-than, return zero if they are equal, or return
 a positive value for greater-than. For example, we can do:
 
     >>> def numeric_compare(x, y):
-            return x - y
-    >>> sorted([5, 2, 4, 1, 3], cmp=numeric_compare)
+    ...     return x - y
+    >>> sorted([5, 2, 4, 1, 3], cmp=numeric_compare) # doctest: +SKIP
     [1, 2, 3, 4, 5]
 
 Or you can reverse the order of comparison with:
 
     >>> def reverse_numeric(x, y):
-            return y - x
-    >>> sorted([5, 2, 4, 1, 3], cmp=reverse_numeric)
+    ...     return y - x
+    >>> sorted([5, 2, 4, 1, 3], cmp=reverse_numeric) # doctest: +SKIP
     [5, 4, 3, 2, 1]
 
 When porting code from Python 2.x to 3.x, the situation can arise when you have
@@ -244,6 +244,12 @@ function. The following wrapper makes that easy to do::
 
 To convert to a key function, just wrap the old comparison function:
 
+.. testsetup::
+
+    from functools import cmp_to_key
+
+.. doctest::
+
     >>> sorted([5, 2, 4, 1, 3], key=cmp_to_key(reverse_numeric))
     [5, 4, 3, 2, 1]