Python Set

The Most Pythonic Way to Compare Two Lists in Python

Problem: Given are two lists l1 and l2. You want to perform either of the following: 1. Boolean Comparison: Compare the lists element-wise and return True if your comparison metric returns True for all pairs of elements, and otherwise False. 2. Difference: Find the difference of elements in the first list but not in the …

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List Difference | The Most Pythonic Way

Short answer: The most Pythonic way to compute the difference between two lists l1 and l2 is the list comprehension statement [x for x in l1 if x not in set(l2)]. This works even if you have duplicate list entries, it maintains the original list ordering, and it’s efficient due to the constant runtime complexity …

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The Most Pythonic Way to Check if Two Unordered Lists Are Identical

To check if two unordered lists x and y are identical, compare the converted sets with set(x) == set(y). However, this loses all information about duplicated elements. To consider duplicates, compare the sorted lists with sorted(x) == sorted(y). Due to the efficient merge-sort-like implementation of the sorted() function, this is quite fast for almost-sorted lists. …

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The Most Pythonic Way to Check If a List Contains an Element

The standard way of checking if an element exists in a list is to use the in keyword. For example, ‘Alice’ in [1, ‘Alice’, 3] will return True while the same returns False for ‘Bob’. If you need to check more complicated conditions, use the any(condition(x) for x in list) function with a generator expression. …

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string.join(list) vs list.join(string) | Why Python’s Creators Chose The Former

If you’re like me, you may have asked yourself the following question: Why is it string.join(list) instead of list.join(string) in Python? 🙄 The join method works with any iterable, not just with lists. Therefore, you’d have to implement it in hundreds of classes instead of just one (in the string class). Additionally, join() works only …

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How to Combine Two Python Lists and Remove Duplicates in Second List?

Problem: Given two lists [1, 2, 2, 4] and [2, 5, 5, 5, 6]. How do you combine those lists to the new list [1, 2, 2, 4, 5, 6] by removing the duplicates in the second list? Note: You want to remove all duplicates in the second list and the elements in the second …

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How to Intersect Multiple Sets in Python?

To intersect multiple sets, stored in a list l, use the Python one-liner l.pop().intersection(*l) that takes the first set from the list, calls the intersection() method on it, and passes the remaining sets as arguments by unpacking them from the list. A set is a unique collection of unordered elements. The intersection operation creates a …

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How to Union Multiple Sets in Python?

The most efficient way to join multiple sets (stored in a list of sets), use the Python one-liner set().union(*list) that creates a new set object, calls the union() method on the new object, and unpacks all sets from the list of sets into the union() method’s argument list. A set is a unique collection of …

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Python List to Set Conversion [Interactive Guide]

Do you have a list but you want to convert it to a Python set? No problem! Use the set(…) constructor and pass the list object as an argument. For example, if you have a list of strings friends, you can convert it to a set using the call set(friends). Here’s an example code snippet: …

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