Why do some methods of built-in types operate in-place and some don't?

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dog = 'penny'

dog_names = ['pete', 'luke', 'shane']

Why does Python return an output of Penny for dog.title() but None for dog_names.remove('shane')? Why can I not print the list dog_name with the method remove while I can use the method title on dog?

I understand that I get None because dog_name.remove has no return, but how does dog.title have a return?

The title() function is a pre-defined function in Python which is used to covert the first character of the string into uppercase and the remaining characters into lowercase and return a new string. in your example if you run print(dog) you can see that penny is all lowercase, but if you run print(dog.title()) you can see that the first letter in Penny which is P is uppercase and the remaining is lowercase

Built-in Types — Python 3.8.5 documentation, Some operations are supported by several object types; in particular, practically all The reverse() method modifies the sequence in place for economy of space when The methods on bytes and bytearray objects don't accept strings as their � As an example, if we don't use extension methods, we might create an Engine or Query class to do the work of executing a query on a SQL Server that may be called from multiple places in our code. However we can instead extend the System.Data.SqlClient.SqlConnection class using extension methods to perform that query from anywhere we have a

4. Built-in Types — Python 3.3.7 documentation, Some operations are supported by several object types; in particular, The reverse() method modifies the sequence in place for economy of space when of mutable containers that don't support slicing operations (such as dict and set). If a picture can speak a thousand words, in a project, as built drawings can speak a thousand construction processes. But in all seriousness, with the hundreds and thousands of steps and documents needed to complete just one project, as builts might be overlooked for their importance.

A function/method in any programming language performs a specific task. A task could be performed on the inputs passed to the function. After performing the task, the function may want to give the result back to the caller of the function. It may do that by:

  1. By modifying the parameters passed to it or By altering the object on which method was called. (For example, remove() method of list data type)
  2. By returning the result to the caller. (title() method)
  3. A combination of (1) and (2)

Your remove() method doesn't return anything back to the caller. Instead it just deletes an element from the list. To print the list after removing an element:


Classes - Object-Oriented Programming in Python, We have already used the methods of some built-in objects, like strings and lists. We don't have to assign it to an intermediate variable before using it as a same operation on all of them, as we do in this example which uses a dictionary: when a class attribute is of a mutable type – because if we modify it in-place, we� Strings do have a length method: __len__() The protocol in Python is to implement this method on objects which have a length and use the built-in len() function, which calls it for you, similar to the way you would implement __iter__() and use the built-in iter() function (or have the method called behind the scenes for you) on objects which are iterable.

4. Introducing Python Object Types, In fact, unless you have a need for special processing that built-in types don't Table 4-1 previews Python's built-in object types and some of the syntax used to because strings are immutable in Python—they cannot be changed in-place after For example, the string find method is the basic substring search operation (it� Technically speaking, a Python iterator object must implement two special methods, __iter__() and __next__(), collectively called the iterator protocol. An object is called iterable if we can get an iterator from it. Most built-in containers in Python like: list, tuple, string etc. are iterables.

Special Method Names, New in Python 3, since the bytes type was introduced. (In this case, it's just a hard-coded string, but you would normally do some sort of If you don't define an in-place method for a particular operation, Python will try the methods. Format Specification Mini-Language; Python data model; Built-in types; PEP 357: � Groups of the same size don’t always work for all students. Keep an eye on what types of arrangements different learners respond to best. Here are some options for adapting the arrangement of students during classtime: Let your student work in a group of three when most of her classmates work in groups of four or five.

Lists, mutability, and in-place methods, A list is a Python object that represents am ordered sequence of other objects. If loops and also, what it means for a method to perform an “in-place” operation on an object. Lists can contain objects of any type, including other lists: Non- in-place methods don't alter their object; instead, they return a copy of that object: These methods provides special syntactic features or does special things. For example, __file__ indicates the location of Python file, __eq__ is executed when a == b expression is excuted. A user of course can make custom special method, it is very rare case, but often might modify the some built-in special methods. (e.g.

  • docs.python.org/3/library/stdtypes.html#str.title
  • list.remove() modifies the list in-place, it is convention for all methods that modify an object in-place to return None
  • Does this answer your question? Inplace functions in Python
  • A better duplicate target: Why some methods change the object permanently while others don't?