infinite loop

When I try to execute this code: https://gist.github.com/kmike/91ef29a3fd2b94ff8b47a5a9ebfa7be2 in an IPython cell (both terminal and notebook), IPython goes to an infinite loop. Code just defines a nested dict; there are unicode symbols. Here is the traceback on interruption:

ERROR:tornado.general:Uncaught exception in ZMQStream callback
Traceback (most recent call last):
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/zmq/eventloop/zmqstream.py", line 432, in _run_callback
    callback(*args, **kwargs)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/tornado/stack_context.py", line 277, in null_wrapper
    return fn(*args, **kwargs)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/ipykernel/kernelbase.py", line 283, in dispatcher
    return self.dispatch_shell(stream, msg)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/ipykernel/kernelbase.py", line 233, in dispatch_shell
    handler(stream, idents, msg)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/ipykernel/kernelbase.py", line 399, in execute_request
    user_expressions, allow_stdin)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/ipykernel/ipkernel.py", line 208, in do_execute
    res = shell.run_cell(code, store_history=store_history, silent=silent)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/ipykernel/zmqshell.py", line 537, in run_cell
    return super(ZMQInteractiveShell, self).run_cell(*args, **kwargs)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/IPython/core/interactiveshell.py", line 2654, in run_cell
    cell = self.input_transformer_manager.transform_cell(raw_cell)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/IPython/core/inputsplitter.py", line 659, in transform_cell
    self.push(cell)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/IPython/core/inputsplitter.py", line 702, in push
    out = self.push_line(line)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/IPython/core/inputsplitter.py", line 729, in push_line
    line = self.assemble_python_lines.push(line)
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/IPython/core/inputtransformer.py", line 138, in push
    for intok in self.tokenizer:
  File "/Users/kmike/envs/deep-deep/lib/python3.6/site-packages/IPython/utils/tokenize2.py", line 508, in _tokenize
    pseudomatch = pseudoprog.match(line, pos)
KeyboardInterrupt

I have latest ipython[notebook] installed, with all dependencies upgraded as well.

[takluyver]

It’s not actually infinite, just very slow. There’s some code in current released versions that’s O(N^2) on the number of lines in an executed cell. #10898 improves on this, but hasn’t been released yet.

Even in master, it takes a while to execute, though. IPython is not a good environment for running very long pieces of code, because we have to go through the code to identify and transform IPython special syntax (%magic and !system commands and so on). We may be able to make that more efficient, but it’s probably always going to be slower than putting it in a .py file and using from currency_data import CURRENCIES.

[kmike]

Awesome, thanks @takluyver and @Carreau!