Blog
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Python *args: Accepting any number of positional arguments
Want your Python function to take any number of positional args? Use *args: – Can be any name, but args is traditional– The * is only in the function definition– It’s a tuple– Don’t grab elements by index; iterate over them– It might be empty– Pronounce it “splat args”
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Positional vs keyword arguments in Python function calls
How are arguments assigned to parameters when calling a Python function? There are two ways: – Positional, based on order– Keyword, i.e., name=value, assigned by name Want to mix and match? Fine, but all positional must come before all keyword:
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Python 3.15 lazy imports: Deferring module load until first use
Every import in Python executes the module, from start to finish. Meaning? Big modules slow down your program’s startup time. Coming in Python 3.15 this October: “lazy import”, which delays the load until a name is used: lazy import MODULElazy from MODULE import NAME
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Python dict keys: Why custom objects work but lists don’t
Mutable builtins in Python cannot be dict keys. But your (mutable) classes can!
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Python dict keys must be hashable: Why lists don’t work
You can’t use a list as a Python dict key: Why not? Dicts run “hash” on a key to choose a pair’s storage location. To avoid pairs getting lost, mutable builtins (list, set, dict) cannot be used as dict keys.
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Do you teach Python? Then check out course-setup
TL;DR: If you teach Python, then you should check out course-setup (https://pypi.org/project/course-setup/) at PyPI! I’ve been teaching Python and Pandas for many years. And while I started my teaching career like many other instructors, with slides, I quickly discovered that it was better for my students — and for me! — to replace them with…
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Pandas str.split: Get the first item of a comma-separated column
A Python Pandas column contains comma-separated values. How can you get the first of those? First, break each string into a list: Then use .str[0] to grab the first element from the resulting list:
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Pandas str.isdigit: Checking whether strings contain only digits
Want to check whether a Python Pandas string series only contains digits? Use str.isdigit: This returns a boolean series, with df’s index. You can then convert the digit-containing strings to integers:
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Pandas string slicing: Extracting substrings with .str.slice
Want to retrieve a slice from a string column in your Python Pandas data frame? Use .str.slice:
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Pandas .str.get: Retrieving characters from string columns
Want to retrieve from a string column in your Python Pandas data frame? Use .str.get: But wait: You can use [], in place of .get: