Why Does Python Code Use Len() Function Instead of a Length Method

Why does Python code use len() function instead of a length method?

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.

See Emulating container types for more information.

Here's a good read on the subject of protocols in Python: Python and the Principle of Least Astonishment

Java EE -- is it just fluff or the real stuff?

The key differentiator that Java EE offers over the LAMP stack can be boiled down to a single word. Transactions.

Most smaller systems simply rely on the transaction system supplied by the database, and for many applications that is (obviously) quite satisfactory.

But each Java EE server includes a distributed transaction manager. This lets you do more complicated things, across diverse systems, safely and reliably.

The most simple example of this is the simple scenario of taking a record from a database, putting it on a messaging queue (JMS), and then deleting that row from the database. This simple case involves two separate systems, and can not reliably be done out side of a transaction. For example, you can put the row on to the message queue, but (due to a system failure) not remove the row from the database. You can see how having a transaction with the JMS provider and a separate transaction with the database doesn't really solve the problem, as the transactions are not linked together.

Obviously this simple scenario can be worked around, a dealt with, etc. The nice thing with Java EE, though, is that you don't have to deal with these kind of issues -- the container gets to deal with them.

And, again, not every problem requires this level o transaction handling. But for those that do, it's invaluable. And once you get used to using them, you'll find the transaction management of a Java EE server to be a great asset.

Why is Python's 'len' function faster than the len method?

The builtin len() function does not look up the .__len__ attribute. It looks up the tp_as_sequence pointer, which in turn has a sq_length attribute.

The .__len__ attribute on built-in objects is indirectly mapped to the same slot, and it is that indirection (plus the attribute lookup) that takes more time.

For Python-defined classes, the type object looks up the .__len__ method when the sq_length is requested.

Difference between len() and .len()?

len is a function to get the length of a collection. It works by calling an object's __len__ method. __something__ attributes are special and usually more than meets the eye, and generally should not be called directly.

It was decided at some point long ago getting the length of something should be a function and not a method code, reasoning that len(a)'s meaning would be clear to beginners but a.len() would not be as clear. When Python started __len__ didn't even exist and len was a special thing that worked with a few types of objects. Whether or not the situation this leaves us makes total sense, it's here to stay.

What is the relation of len() function with int data type?

The len function returns the length of the string, which happens to be an integer.

When the object is a string, the len() function returns the number of
characters in the string.

Learn more about the len function here: https://www.w3schools.com/python/ref_func_len.asp

To clear up things :-

input_string = input("what is your name?")
input_string_length = len(input_string)

print(type(input_string)) # <class 'str'>
print(type(input_string_length)) # <class int>

Thus, as you can see, the input string is not affected in any way and is not converted to the int type.

Why does python list does not have len() method

likely just because its redundant when we already have and are use to len() maybe you could add a .len() method :)

there is a a_list.__len__()

Cost of len() function

It's O(1) (constant time, not depending of actual length of the element - very fast) on every type you've mentioned, plus set and others such as array.array.

Why does my len() code in python not provide the correct length of a string?

random.sample(word_list, 1) returns single item list like ["sparkle"] and you're converting it into str so it adds [""] around the word so word becomes '["sparkle"]'

I think you need:

import random

word_list = ['tiger','dog','cake','disney','donut','rose','clouds','movies','sparkle','yoga','walrus','candle','mango','taco','flowers']

word = random.sample(word_list, 1)
word_len = len(word[0])

print(word, word_len)

Output:

['sparkle'] 7

lower versus length syntax in python?

lower is a string method, that is, a function built in to the string object itself. It only applies to string objects.

len is a built in function, that is, a function available in the top namespace. It can be called on many different objects (strings, lists, dicts) and isn't unique to strings.