https://en.netcup.nllk.net/blog/categories/python/ Recent content in python on netcup hosting blog Hugo -- gohugo.io en Mon, 31 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0058-python-concatenate-lists/ Mon, 31 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0058-python-concatenate-lists/ This article shows how to concatenate two lists in Python and why + and += behave differently for anyone else holding the list. https://en.netcup.nllk.net/blog/post/0060-python-copy-file/ Mon, 31 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0060-python-copy-file/ This article shows how to copy a file in Python, what each shutil function preserves, and the Path.copy method added in Python 3.14. https://en.netcup.nllk.net/blog/post/0059-python-mutable-default-argument/ Mon, 31 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0059-python-mutable-default-argument/ This article explains why a mutable default argument in Python is shared between calls, where the value actually lives, and when None is not enough. https://en.netcup.nllk.net/blog/post/0040-python-ternary-operator/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0040-python-ternary-operator/ This article shows Python's ternary conditional expression, why the older and/or and tuple tricks are worse, and where the precedence catches you out. https://en.netcup.nllk.net/blog/post/0046-python-slicing/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0046-python-slicing/ This article explains Python's slice syntax, why slices never raise IndexError and why a slice copy is only shallow. https://en.netcup.nllk.net/blog/post/0048-python-loop-index/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0048-python-loop-index/ This article shows how to get the index in a Python for loop with enumerate, and what goes wrong when you modify the list while iterating. https://en.netcup.nllk.net/blog/post/0055-python-check-list-empty/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0055-python-check-list-empty/ This article shows how to check whether a list is empty in Python, what else the idiomatic check catches, and why it does not work on generators. https://en.netcup.nllk.net/blog/post/0049-python-create-directory/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0049-python-create-directory/ This article shows how to create a directory and any missing parent directories in Python, and why checking whether it exists first is a race condition. https://en.netcup.nllk.net/blog/post/0044-python-list-index/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0044-python-list-index/ This article shows how to find the index of an item in a Python list, how to handle a missing item, and when to stop using list.index() altogether. https://en.netcup.nllk.net/blog/post/0045-python-flatten-list/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0045-python-flatten-list/ This article shows how to flatten a list of lists in Python, why sum(nested, []) is quadratic and how a recursive flatten crashes on strings. https://en.netcup.nllk.net/blog/post/0042-python-current-time/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0042-python-current-time/ This article shows how to get the current date and time in Python, why datetime.now() alone is not enough and why utcnow() is now deprecated. https://en.netcup.nllk.net/blog/post/0051-python-pandas-iterate-rows/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0051-python-pandas-iterate-rows/ This article shows how to iterate over rows in a Pandas DataFrame, how much it costs compared to vectorising, and why writing to the row does nothing. https://en.netcup.nllk.net/blog/post/0039-python-merge-dicts/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0039-python-merge-dicts/ This article shows how to merge two dictionaries in Python in a single expression, and why the result is shallower than you might expect. https://en.netcup.nllk.net/blog/post/0052-python-pass-by-reference/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0052-python-pass-by-reference/ This article explains how Python passes arguments, why the mutable-versus-immutable framing is misleading and what += really does. https://en.netcup.nllk.net/blog/post/0054-python-pandas-rename-columns/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0054-python-pandas-rename-columns/ This article shows how to rename Pandas DataFrame columns, why rename() fails silently on a typo and how duplicate column names change what df['x'] returns. https://en.netcup.nllk.net/blog/post/0037-python-run-shell-command/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0037-python-run-shell-command/ This article shows how to call an external program from Python using subprocess.run, and what shell=True really costs you. https://en.netcup.nllk.net/blog/post/0053-python-sort-dict-by-value/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0053-python-sort-dict-by-value/ This article shows how to sort a dictionary by value in Python, how to break ties, and how to sort by one field descending and another ascending. https://en.netcup.nllk.net/blog/post/0043-python-split-list-chunks/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0043-python-split-list-chunks/ This article shows how to split a list into chunks in Python using itertools.batched, and why the old zip_longest recipe gives a different result. https://en.netcup.nllk.net/blog/post/0047-python-upgrade-all-packages/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0047-python-upgrade-all-packages/ This article shows how to upgrade all installed packages with pip, why the popular one-liner is fragile and how upgrading one at a time can break your environment. https://en.netcup.nllk.net/blog/post/0056-python-global-variable/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0056-python-global-variable/ This article explains the global keyword in Python, why assigning to a name makes it local for the whole function, and when you do not need global at all. https://en.netcup.nllk.net/blog/post/0057-python-str-vs-repr/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0057-python-str-vs-repr/ This article explains the difference between __str__ and __repr__ in Python, which one containers use, and why you should define __repr__ first. https://en.netcup.nllk.net/blog/post/0050-python-staticmethod-classmethod/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0050-python-staticmethod-classmethod/ This article explains the difference between @staticmethod and @classmethod in Python, and why alternative constructors have to be classmethods. https://en.netcup.nllk.net/blog/post/0038-python-name-main/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0038-python-name-main/ This article explains what if __name__ == "__main__": does in Python, why you want it, and the trap of a module being loaded twice. https://en.netcup.nllk.net/blog/post/0041-python-metaclasses/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0041-python-metaclasses/ This article explains what a metaclass is in Python, when its hooks run, and why __init_subclass__ is usually the better answer. https://en.netcup.nllk.net/blog/post/0036-python-yield-keyword/ Sat, 29 Aug 2026 00:00:00 +0000 https://en.netcup.nllk.net/blog/post/0036-python-yield-keyword/ This article explains what the yield keyword does in Python, what a generator is and where the memory savings actually come from.