Last round of adapting style of documenting argument default values.
diff --git a/Doc/library/warnings.rst b/Doc/library/warnings.rst
index 260323e..36d47ad 100644
--- a/Doc/library/warnings.rst
+++ b/Doc/library/warnings.rst
@@ -234,7 +234,7 @@
 -------------------
 
 
-.. function:: warn(message[, category[, stacklevel]])
+.. function:: warn(message, category=None, stacklevel=1)
 
    Issue a warning, or maybe ignore it or raise an exception.  The *category*
    argument, if given, must be a warning category class (see above); it defaults to
@@ -253,7 +253,7 @@
    of the warning message).
 
 
-.. function:: warn_explicit(message, category, filename, lineno[, module[, registry[, module_globals]]])
+.. function:: warn_explicit(message, category, filename, lineno, module=None, registry=None, module_globals=None)
 
    This is a low-level interface to the functionality of :func:`warn`, passing in
    explicitly the message, category, filename and line number, and optionally the
@@ -270,7 +270,7 @@
    sources).
 
 
-.. function:: showwarning(message, category, filename, lineno[, file[, line]])
+.. function:: showwarning(message, category, filename, lineno, file=None, line=None)
 
    Write a warning to a file.  The default implementation calls
    ``formatwarning(message, category, filename, lineno, line)`` and writes the
@@ -282,7 +282,7 @@
    try to read the line specified by *filename* and *lineno*.
 
 
-.. function:: formatwarning(message, category, filename, lineno[, line])
+.. function:: formatwarning(message, category, filename, lineno, line=None)
 
    Format a warning the standard way.  This returns a string which may contain
    embedded newlines and ends in a newline.  *line* is a line of source code to
@@ -291,7 +291,7 @@
    *lineno*.
 
 
-.. function:: filterwarnings(action[, message[, category[, module[, lineno[, append]]]]])
+.. function:: filterwarnings(action, message='', category=Warning, module='', lineno=0, append=False)
 
    Insert an entry into the list of :ref:`warnings filter specifications
    <warning-filter>`.  The entry is inserted at the front by default; if
@@ -303,7 +303,7 @@
    everything.
 
 
-.. function:: simplefilter(action[, category[, lineno[, append]]])
+.. function:: simplefilter(action, category=Warning, lineno=0, append=False)
 
    Insert a simple entry into the list of :ref:`warnings filter specifications
    <warning-filter>`.  The meaning of the function parameters is as for
@@ -322,7 +322,7 @@
 Available Context Managers
 --------------------------
 
-.. class:: catch_warnings([\*, record=False, module=None])
+.. class:: catch_warnings(\*, record=False, module=None)
 
     A context manager that copies and, upon exit, restores the warnings filter
     and the :func:`showwarning` function.