Fix cpaste documentation

- The code was example was invalid Python3
- IPython magics are supported
- Added example using a magic

Closes  #12930

IPython/terminal/magics.py

@@ -1,203 +1,213 b''
 """Extra magics for terminal use."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 
 from logging import error
 import os
 import sys
 
 from IPython.core.error import TryNext, UsageError
 from IPython.core.magic import Magics, magics_class, line_magic
 from IPython.lib.clipboard import ClipboardEmpty
 from IPython.utils.text import SList, strip_email_quotes
 from IPython.utils import py3compat
 
 def get_pasted_lines(sentinel, l_input=py3compat.input, quiet=False):
     """ Yield pasted lines until the user enters the given sentinel value.
     """
     if not quiet:
         print("Pasting code; enter '%s' alone on the line to stop or use Ctrl-D." \
               % sentinel)
         prompt = ":"
     else:
         prompt = ""
     while True:
         try:
             l = l_input(prompt)
             if l == sentinel:
                 return
             else:
                 yield l
         except EOFError:
             print('<EOF>')
             return
 
 
 @magics_class
 class TerminalMagics(Magics):
     def __init__(self, shell):
         super(TerminalMagics, self).__init__(shell)
 
     def store_or_execute(self, block, name):
         """ Execute a block, or store it in a variable, per the user's request.
         """
         if name:
             # If storing it for further editing
             self.shell.user_ns[name] = SList(block.splitlines())
             print("Block assigned to '%s'" % name)
         else:
             b = self.preclean_input(block)
             self.shell.user_ns['pasted_block'] = b
             self.shell.using_paste_magics = True
             try:
                 self.shell.run_cell(b)
             finally:
                 self.shell.using_paste_magics = False
 
     def preclean_input(self, block):
         lines = block.splitlines()
         while lines and not lines[0].strip():
             lines = lines[1:]
         return strip_email_quotes('\n'.join(lines))
 
     def rerun_pasted(self, name='pasted_block'):
         """ Rerun a previously pasted command.
         """
         b = self.shell.user_ns.get(name)
 
         # Sanity checks
         if b is None:
             raise UsageError('No previous pasted block available')
         if not isinstance(b, str):
             raise UsageError(
                 "Variable 'pasted_block' is not a string, can't execute")
 
         print("Re-executing '%s...' (%d chars)"% (b.split('\n',1)[0], len(b)))
         self.shell.run_cell(b)
 
     @line_magic
     def autoindent(self, parameter_s = ''):
         """Toggle autoindent on/off (deprecated)"""
         self.shell.set_autoindent()
         print("Automatic indentation is:",['OFF','ON'][self.shell.autoindent])
 
     @line_magic
     def cpaste(self, parameter_s=''):
         """Paste & execute a pre-formatted code block from clipboard.
 
         You must terminate the block with '--' (two minus-signs) or Ctrl-D
         alone on the line. You can also provide your own sentinel with '%paste
         -s %%' ('%%' is the new sentinel for this operation).
 
         The block is dedented prior to execution to enable execution of method
         definitions. '>' and '+' characters at the beginning of a line are
         ignored, to allow pasting directly from e-mails, diff files and
         doctests (the '...' continuation prompt is also stripped).  The
         executed block is also assigned to variable named 'pasted_block' for
         later editing with '%edit pasted_block'.
 
         You can also pass a variable name as an argument, e.g. '%cpaste foo'.
         This assigns the pasted block to variable 'foo' as string, without
         dedenting or executing it (preceding >>> and + is still stripped)
 
         '%cpaste -r' re-executes the block previously entered by cpaste.
         '%cpaste -q' suppresses any additional output messages.
 
         Do not be alarmed by garbled output on Windows (it's a readline bug).
         Just press enter and type -- (and press enter again) and the block
         will be what was just pasted.
 
-        IPython statements (magics, shell escapes) are not supported (yet).
+        Shell escapes are not supported (yet).
 
         See also
         --------
         paste: automatically pull code from clipboard.
 
         Examples
         --------
         ::
 
           In [8]: %cpaste
           Pasting code; enter '--' alone on the line to stop.
           :>>> a = ["world!", "Hello"]
-          :>>> print " ".join(sorted(a))
+          :>>> print(" ".join(sorted(a)))
           :--
           Hello world!
+
+        ::
+          In [8]: %cpaste
+          Pasting code; enter '--' alone on the line to stop.
+          :>>> %alias_magic t timeit
+          :>>> %t -n1 pass
+          :--
+          Created `%t` as an alias for `%timeit`.
+          Created `%%t` as an alias for `%%timeit`.
+          354 ns ± 224 ns per loop (mean ± std. dev. of 7 runs, 1 loop each)
         """
         opts, name = self.parse_options(parameter_s, 'rqs:', mode='string')
         if 'r' in opts:
             self.rerun_pasted()
             return
 
         quiet = ('q' in opts)
 
         sentinel = opts.get('s', u'--')
         block = '\n'.join(get_pasted_lines(sentinel, quiet=quiet))
         self.store_or_execute(block, name)
 
     @line_magic
     def paste(self, parameter_s=''):
         """Paste & execute a pre-formatted code block from clipboard.
 
         The text is pulled directly from the clipboard without user
         intervention and printed back on the screen before execution (unless
         the -q flag is given to force quiet mode).
 
         The block is dedented prior to execution to enable execution of method
         definitions. '>' and '+' characters at the beginning of a line are
         ignored, to allow pasting directly from e-mails, diff files and
         doctests (the '...' continuation prompt is also stripped).  The
         executed block is also assigned to variable named 'pasted_block' for
         later editing with '%edit pasted_block'.
 
         You can also pass a variable name as an argument, e.g. '%paste foo'.
         This assigns the pasted block to variable 'foo' as string, without
         executing it (preceding >>> and + is still stripped).
 
         Options:
 
           -r: re-executes the block previously entered by cpaste.
 
           -q: quiet mode: do not echo the pasted text back to the terminal.
 
         IPython statements (magics, shell escapes) are not supported (yet).
 
         See also
         --------
         cpaste: manually paste code into terminal until you mark its end.
         """
         opts, name = self.parse_options(parameter_s, 'rq', mode='string')
         if 'r' in opts:
             self.rerun_pasted()
             return
         try:
             block = self.shell.hooks.clipboard_get()
         except TryNext as clipboard_exc:
             message = getattr(clipboard_exc, 'args')
             if message:
                 error(message[0])
             else:
                 error('Could not get text from the clipboard.')
             return
         except ClipboardEmpty as e:
             raise UsageError("The clipboard appears to be empty") from e
 
         # By default, echo back to terminal unless quiet mode is requested
         if 'q' not in opts:
             write = self.shell.write
             write(self.shell.pycolorize(block))
             if not block.endswith('\n'):
                 write('\n')
             write("## -- End pasted text --\n")
 
         self.store_or_execute(block, name)
 
     # Class-level: add a '%cls' magic only on Windows
     if sys.platform == 'win32':
         @line_magic
         def cls(self, s):
             """Clear screen.
             """
             os.system("cls")