Tag: Python
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Python `__all__`: Blocking wildcard imports with a fake name
Want to guarantee that no one can run “from .. import *” on your Python module? Include a non-existent name in the __all__ list: Using “from .. import *” on this module will result in an error!
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Python __all__: Controlling which names import * exports
Writing a Python module? Want to control which names are exported via “from .. import *”? Define __all__, a list of strings indicating which names will be exported via “import *”:
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Wildcard imports in Python: Why from module import * is a bad idea
Using many names from a Python module? Import them all: Wait: This is usually a TERRIBLE idea! • Potential namespace collisions• Less readable code• Module upgrades affect globals in your program I know, it’s tempting — but don’t!
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Python even/odd checks: Using truthiness instead of == 0
Python trick: 0 is falsy, 1 is truthy. Use this for even/odd checks: No need for “if n % 2 == 0” — just use the truthiness!
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Counting NaN values in a Pandas DataFrame with isna and sum
How many NaNs in a Python Pandas data frame? 1. Use isna, returning a data frame of booleans2. Use sum, returning the number of NaNs in each column3. Use sum again, adding those numbers
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Python division operators: / returns a float, // rounds down
Remember that Python has two division operators:10 / 2 # truediv, returns float: 5.010 // 2 # floordiv, rounds down: 510 / 3 # truediv: 3.333…10 // 3 # floordiv: 3 Note: // with floats returns a float (10.0 // 3 = 3.0)
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Python extended unpacking: Using * to assign leftover values
Unsure how many values you want to unpack in Python? Use * to get a list of flexible length: Note: You can only have one * variable.
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uv version –bump: Increasing your project’s version number
Using uv to manage your Python project, and want to increase the version in pyproject.toml? Use “uv version”, specifying what level to increase: uv version –bump=minor uv version –bump=majoruv version –bump=dev Type “uv version –bump” with no value for full docs.
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Python multi-line comprehensions: Formatting for readability
Make your Python comprehensions easier to read, write, and debug with multiple lines. # better than:[n**2 for n in range(10) if n%2]
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collections.Counter: Counting values in a Python sequence
Want to count values in a Python sequence? Use Counter: Bonus: Counter inherits from dict, getting its methods + operators.