Category: Python
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OrderedDict vs dict: Why equality checks compare order
Why use OrderedDict if Python dicts are now ordered? Because equality checks order too:
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Sorting custom Python objects with __lt__ and __eq__
Make a Python class sortable with __lt__ and __eq__:
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Python str.strip: Removing any characters, not just whitespace
By default, str.strip in Python removes leading/trailing whitespace: It takes an optional argument, naming leading/trailing characters to remove. Great for cleaning strings:
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Dispatch tables in Python: Replace if/elif with a dict of functions
Instead of choosing which Python function to run with if/elif/else, use a dispatch table — a dict with functions as values:
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Python dict insertion order: What happens when you re-add a key
Modern Python dicts remember insertion order: This applies in for loops, too!
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Python defaultdict: Pass a factory function, not a value
Using Python defaultdict? Don’t pass a value: Pass a function that returns the default:
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Python positional-only parameters: Fixing **kwargs conflicts
Your Python function takes a filename and **kwargs. But this raises an error, since “filename” is passed twice: Solution: Set filename to be positional only: Now any keyword argument works!
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Python str.split and rsplit: Splitting strings with maxsplit
Break a Python string into a list of strings with str.split: Limit splits with maxsplit: Or split from the right, with a limit:
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%xmode in IPython: Shortening long Python tracebacks
Tired of super-long Python Pandas backtraces in Jupyter or IPython? Use the %xmode magic method: %xmode Minimal Now you just see the error, not 50 lines of library internals. You can also set it to Plain, Context, or Verbose.
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Pandas columns overlap error: Fixing join with lsuffix and rsuffix
Joining Python Pandas DataFrames with overlapping columns? You’ll hit: ValueError: columns overlap but no suffix specified Fix with lsuffix and rsuffix: Now the columns are: x_left, x_right, y_left, y_right Problem solved!