Python

Returning a list in Python is as simple as using the return statement from within a function, followed by an object of type list. For example: return [1, 2, 3]. This will return a list containing elements 1, 2, and 3. Return a list directly Returning a list in Python can be done by simply … Read more

This error occurs when you try to iterate over an integer in Python. To fix this, make sure anything after the in operator in Python is an iterable, such as a list. If you’re trying to use the integer to determine the number of times you’d like a for loop to run, use the range() … Read more

In Python, semicolons (;) can be used to join two separate lines on a single line, and for loops can have the body of the loop on the same line after the colon (:). Alternatively, you can use list comprehension to put a for loop on a single line. Simply put it on one line … Read more

To copy a list of lists in Python, or a list containing any other complex types, use the deepcopy function in the copy module. Example: import copy; list2 = copy.deepcopy(list1). Can I just use list.copy? It might be tempting to just use the built-in .copy() method for a Python list to make a copy of … Read more

To print an exception in Python, you can either just call print(e) directly on the exception object, or use traceback.print_exc() to print the entire stack trace. You’ll have to import the traceback module to use the second option, though. How to print just the exception message Printing exceptions is easy in Python. Since they all … Read more

To check if a string doesn’t contain a substring in Python, just use the in operator. For example: “foo” not in “Hello world” will return True, i.e., the string “foo” isn’t found in the string “Hello world”. Alternatively, you can use the re library or the .rfind() method of Python’s built-in string class to do … Read more

This error means you tried to call .get on a string. The str type in Python doesn’t have that method. You probably meant to call .get on a dict instead. To fix this, make sure the variable you’re calling .get on is a dict and not a string. The dict type in Python has a … Read more

The Python error “TypeError: str returned non-string (type NoneType)” means you aren’t returning a string from your class’ __str__ method. To fix this, make sure you’re actually returning a string. Python has methods called “dunder” methods, which is shorthand for “double underscore”. They are special methods you can add to your classes to do things … Read more

This error means you gave two arguments to list.extend(), which only takes one. You probably are trying to add two items to the list. The fix is simple, just wrap those two items in brackets ([]) to make them a list, and therefore only one argument. Problem: you passed 2 arguments to list.extend() If you … Read more

This error means that you’re trying to call list.append() with two arguments. You might be trying to add two items to the list at once, in which case you should use list.extend() or simply call list.append() twice. Problem: you are passing two arguments to append If you have a list that you want to add … Read more