Updating the support files

Author: AllenDowney

thinkpython.py

@@ -2,21 +2,6 @@
 import io
 import re
 
-from IPython.core.magic import register_cell_magic
-from IPython.core.magic_arguments import argument, magic_arguments, parse_argstring
-
-
-def traceback(mode):
- """Set the traceback mode.
-
- mode: string
- """
- with contextlib.redirect_stdout(io.StringIO()):
- get_ipython().run_cell(f'%xmode {mode}')
- 
-
-traceback('Minimal')
-
 
 def extract_function_name(text):
  """Find a function definition and return its name.
@@ -34,61 +19,75 @@ def extract_function_name(text):
  return None
 
 
-@register_cell_magic
-def add_method_to(args, cell):
+# the functions that define cell magic commands are only defined
+# if we're running in Jupyter.
 
- # get the name of the function defined in this cell
- func_name = extract_function_name(cell)
- if func_name is None:
- return f"This cell doesn't define any new functions."
+try:
+ from IPython.core.magic import register_cell_magic
+ from IPython.core.magic_arguments import argument, magic_arguments, parse_argstring
 
- # get the class we're adding it to
- namespace = get_ipython().user_ns
- class_name = args
- cls = namespace.get(class_name, None)
- if cls is None:
- return f"Class '{class_name}' not found."
+ @register_cell_magic
+ def add_method_to(args, cell):
 
- # save the old version of the function if it was already defined
- old_func = namespace.get(func_name, None)
- if old_func is not None:
- del namespace[func_name]
+  # get the name of the function defined in this cell
+  func_name = extract_function_name(cell)
+  if func_name is None:
+  return f"This cell doesn't define any new functions."
 
- # Execute the cell to define the function
- get_ipython().run_cell(cell)
+ # get the class we're adding it to
+ namespace = get_ipython().user_ns
+ class_name = args
+ cls = namespace.get(class_name, None)
+ if cls is None:
+ return f"Class '{class_name}' not found."
 
- # get the newly defined function
- new_func = namespace.get(func_name, None)
- if new_func is None:
- return f"This cell didn't define {func_name}."
+  # save the old version of the function if it was already defined
+  old_func = namespace.get(func_name, None)
+  if old_func is not None:
+  del namespace[func_name]
 
- # add the function to the class and remove it from the namespace
- setattr(cls, func_name, new_func)
- del namespace[func_name]
-
- # restore the old function to the namespace
- if old_func is not None:
- namespace[func_name] = old_func
-
- 
-@register_cell_magic
-def expect_error(line, cell):
- try:
+ # Execute the cell to define the function
  get_ipython().run_cell(cell)
- except Exception as e:
- get_ipython().run_cell('%tb')
-
 
+ # get the newly defined function
+ new_func = namespace.get(func_name, None)
+ if new_func is None:
+ return f"This cell didn't define {func_name}."
 
-@magic_arguments()
-@argument('exception', help='Type of exception to catch')
-@register_cell_magic
-def expect(line, cell):
- args = parse_argstring(expect, line)
- exception = eval(args.exception)
- try:
- get_ipython().run_cell(cell)
- except exception as e:
- get_ipython().run_cell("%tb")
-
+ # add the function to the class and remove it from the namespace
+ setattr(cls, func_name, new_func)
+ del namespace[func_name]
 
+ # restore the old function to the namespace
+ if old_func is not None:
+ namespace[func_name] = old_func
+
+ @register_cell_magic
+ def expect_error(line, cell):
+ try:
+ get_ipython().run_cell(cell)
+ except Exception as e:
+ get_ipython().run_cell("%tb")
+
+ @magic_arguments()
+ @argument("exception", help="Type of exception to catch")
+ @register_cell_magic
+ def expect(line, cell):
+ args = parse_argstring(expect, line)
+ exception = eval(args.exception)
+ try:
+ get_ipython().run_cell(cell)
+ except exception as e:
+ get_ipython().run_cell("%tb")
+
+ def traceback(mode):
+ """Set the traceback mode.
+
+ mode: string
+ """
+ with contextlib.redirect_stdout(io.StringIO()):
+ get_ipython().run_cell(f"%xmode {mode}")
+
+ traceback("Minimal")
+except (ImportError, NameError):
+ print("Warning: IPython is not available, cell magic not defined.")