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Diffstat (limited to 'Doc/tutorial/datastructures.rst')
-rw-r--r-- | Doc/tutorial/datastructures.rst | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/Doc/tutorial/datastructures.rst b/Doc/tutorial/datastructures.rst index e008dd8..36abc9c 100644 --- a/Doc/tutorial/datastructures.rst +++ b/Doc/tutorial/datastructures.rst @@ -19,13 +19,13 @@ objects: .. method:: list.append(x) :noindex: - Add an item to the end of the list; equivalent to ``a[len(a):] = [x]``. + Add an item to the end of the list. Equivalent to ``a[len(a):] = [x]``. .. method:: list.extend(L) :noindex: - Extend the list by appending all the items in the given list; equivalent to + Extend the list by appending all the items in the given list. Equivalent to ``a[len(a):] = L``. @@ -40,8 +40,8 @@ objects: .. method:: list.remove(x) :noindex: - Remove the first item from the list whose value is *x*. It is an error if there - is no such item. + Remove the first item from the list whose value is *x*. It is an error if + there is no such item. .. method:: list.pop([i]) @@ -70,13 +70,14 @@ objects: .. method:: list.sort() :noindex: - Sort the items of the list, in place. + Sort the items of the list in place. .. method:: list.reverse() :noindex: - Reverse the elements of the list, in place. + Reverse the elements of the list in place. + An example that uses most of the list methods:: @@ -99,6 +100,10 @@ An example that uses most of the list methods:: >>> a [-1, 1, 66.25, 333, 333, 1234.5] +You might have noticed that methods like ``insert``, ``remove`` or ``sort`` that +modify the list have no return value printed -- they return ``None``. [1]_ This +is a design principle for all mutable data structures in Python. + .. _tut-lists-as-stacks: @@ -480,7 +485,7 @@ using a non-existent key. Performing ``list(d.keys())`` on a dictionary returns a list of all the keys used in the dictionary, in arbitrary order (if you want it sorted, just use -``sorted(d.keys())`` instead). [1]_ To check whether a single key is in the +``sorted(d.keys())`` instead). [2]_ To check whether a single key is in the dictionary, use the :keyword:`in` keyword. Here is a small example using a dictionary:: @@ -677,6 +682,9 @@ interpreter will raise a :exc:`TypeError` exception. .. rubric:: Footnotes -.. [1] Calling ``d.keys()`` will return a :dfn:`dictionary view` object. It +.. [1] Other languages may return the mutated object, which allows method + chaining, such as ``d->insert("a")->remove("b")->sort();``. + +.. [2] Calling ``d.keys()`` will return a :dfn:`dictionary view` object. It supports operations like membership test and iteration, but its contents are not independent of the original dictionary -- it is only a *view*. |