Arguments are passed by assignment. The rationale behind this is twofold: the parameter passed in is actually a reference to an object (but the reference is passed by value) some data types are mutable, but others aren’t So: If you pass a mutable object into a method, the method gets a reference to that same … Read more
Actually, this is not a design flaw, and it is not because of internals or performance. It comes simply from the fact that functions in Python are first-class objects, and not only a piece of code. As soon as you think of it this way, then it completely makes sense: a function is an object … Read more
if not a: print(“List is empty”) Using the implicit booleanness of the empty list is quite pythonic.
Use the + operator to combine the lists: listone = [1, 2, 3] listtwo = [4, 5, 6] joinedlist = listone + listtwo Output: >>> joinedlist [1, 2, 3, 4, 5, 6]
It used to be a required part of a package (old, pre-3.3 “regular package”, not newer 3.3+ “namespace package”). Here’s the documentation. Python defines two types of packages, regular packages and namespace packages. Regular packages are traditional packages as they existed in Python 3.2 and earlier. A regular package is typically implemented as a directory … Read more
You create a new key/value pair on a dictionary by assigning a value to that key d = {‘key’: ‘value’} print(d) # {‘key’: ‘value’} d[‘mynewkey’] = ‘mynewvalue’ print(d) # {‘key’: ‘value’, ‘mynewkey’: ‘mynewvalue’} If the key doesn’t exist, it’s added and points to that value. If it exists, the current value it points to is … Read more
shutil has many methods you can use. One of which is: import shutil shutil.copyfile(src, dst) # 2nd option shutil.copy(src, dst) # dst can be a folder; use shutil.copy2() to preserve timestamp Copy the contents of the file named src to a file named dst. Both src and dst need to be the entire filename of … Read more
Python 3.7+ or CPython 3.6 Dicts preserve insertion order in Python 3.7+. Same in CPython 3.6, but it’s an implementation detail. >>> x = {1: 2, 3: 4, 4: 3, 2: 1, 0: 0} >>> {k: v for k, v in sorted(x.items(), key=lambda item: item[1])} {0: 0, 2: 1, 1: 2, 4: 3, 3: 4} … Read more
Decode the bytes object to produce a string: >>> b”abcde”.decode(“utf-8”) ‘abcde’ The above example assumes that the bytes object is in UTF-8, because it is a common encoding. However, you should use the encoding your data is actually in!
Alex summarized well but, surprisingly, was too succinct. First, let me reiterate the main points in Alex’s post: The default implementation is useless (it’s hard to think of one which wouldn’t be, but yeah) __repr__ goal is to be unambiguous __str__ goal is to be readable Container’s __str__ uses contained objects’ __repr__ Default implementation is … Read more