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$ python -m timeit -s "from permission_vs_forgiveness import test_lbyl" "test_lbyl()"
2000000 loops, best of 5: 155 nsec per loop

$ python -m timeit -s "from permission_vs_forgiveness import test_aff" "test_aff()"
2000000 loops, best of 5: 118 nsec per loop

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# permission_vs_forgiveness.py

class BaseClass:
    hello = "world"

class Foo(BaseClass):
    pass

FOO = Foo()

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try:
    with open("path/to/file.txt", "r") as input_file:
        return input_file.read()
except IOError:
    # Handle the error or just ignore it

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with open("path/to/file.txt") as input_file:
    return input_file.read()

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import os
if os.access("path/to/file.txt", os.R_OK):
    ...

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import os
if os.path.exists("path/to/file.txt"):
    ...

# Or from Python 3.4
from pathlib import Path
if Path("/path/to/file").exists():
    ...

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from IPython.core.magic import register_line_magic


@register_line_magic
def rerunplus(line):
    get_ipython().run_line_magic('load_ext', 'ignore_exceptions')
    get_ipython().run_line_magic('rerun', line)
    get_ipython().run_line_magic('unload_ext', 'ignore_exceptions')

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def unload_ipython_extension(ipython):
    ipython.input_transformers_post = [
        f for f in ipython.input_transformers_post if f.__name__ != 'clean_input'
    ]

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def clean_input(lines):
    new_lines = []
+   lines = combine_multiline(lines)

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def combine_multiline(lines):
    new_lines = []
    for line in lines:
        if line.startswith(' ') and new_lines:
            new_lines[-1] += line
        else:
            new_lines.append(line)
    return new_lines