This is a pretty good list of gotchas, but it's important when writing something targeted at beginners to be as precise and clear as possible. Nearly every sect

This is a pretty good list of gotchas, but it's important when writing something targeted at beginners to be as precise and clear as possible. Nearly every section here either uses terminology poorly, is slightly incorrect, or has difficult examples. Python supports optional function arguments and allows default values to be specified for any optional argument. No, specifying a default is what causes an argument to be optional. it can lead to some confusion when specifying an expression as the default value for an optional function argument. Anything you specify as a default value is an expression. The problem is when the default is mutable. the bar argument is initialized to its default (i.e., an empty list) only the first time that foo() is called No, rather it's when the function is defined. class variables are internally handled as dictionaries As dictionary keys, and that's still only roughly correct. In "Common Mistake #5", he uses both a lambda and array index based looping, neither of which are particularly Pythonic. A better example of where this is a problem in otherwise Pythonic code would be good. In "Common Mistake #6" he uses a lambda in a list comprehension -- for an article of mistakes mostly made by Python beginners, this is going to make it tough to follow the example. In "Common Mistake #7", he describes "recursive imports" where he means "circular imports". In "Common Mistake #8" he refers repeatedly to "stdlib" where he means the Python Standard Library. Someone is going to read that and try to "import stdlib".