Category: Python
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Python line continuation: How parentheses split long lines
Use parentheses to split long Python code across lines: But with parentheses, Python sees it as one line: Or in comprehensions…
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Jupyter memory usage: Why del doesn’t free your DataFrame
Python Jupyter memory quirk: Deleting variables doesn’t always free memory! Use df.head() instead of df to keep big values out of Jupyter’s Out dict.
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Python set subset checks with <=: Spelling Bee word validation
Playing NYT Spelling Bee? Use Python to see if your word only uses allowed letters (ignoring length + center): With sets, <= checks “subset or equal”:
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dict.fromkeys: Why a mutable default value gets shared
Create a Python dict with keys a/b/c and values 0: But don’t do this, since the value will be shared and mutable: {‘a’: [‘x’, ‘y’], ‘b’: [‘x’, ‘y’], ‘c’: [‘x’, ‘y’]} 🤯
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Python round and banker’s rounding: Why round(2.5) returns 2
“round” rounds Python numbers: Remember, .5 goes to the nearest *even* value:
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Python weekend check: Detecting Saturday and Sunday with weekday()
How can you tell if a Python datetime is a weekend (i.e., Saturday or Sunday)? Invoke weekday(). It returns an int; Mon is 0, Sat is 5 and Sun is 6. So:
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Python is vs ==: Object identity and value equality
Consider this Python: Surprised? That’s because “is” is the wrong comparison: • == asks: are these the same value?• is asks: are these the same object? You almost never care about question #2. And so, should rarely use “is”.
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Python numeric literals: Using underscores to group digits
Want to make Python numbers more readable? Use _ between digits (not at the start or end):