CODEWITHSUNDEEP
python
Aryan
Aryan

Reputation: 23

What's this concept called in Python or any programming language?

Suppose name is a type string like name = "test_string"

So the name.lower().endswith('b') is similar to name.lower() and endswith('b'),

like then the alternate code of code1 will be:

Are code1 and code2 the same?.

The doubt is what's the significance of code1? What's that nested "."? I really don't know. Is it like some sort of accessing technical feature in Python or any other programming language?

If so, which languages offer this concept?...

Upvotes: 0

Views: 45

Answers (2)

Amit Pathak
Amit Pathak

Reputation: 1367

Consider an example:

name = "StackOverFLOW"

# Code 1
if name.lower().endswith('w'):
    print("Passed Code 1")

# Code 2
if name.lower() and name.endswith('w'):
    print("Passed Code 2")

The output for the above code is:

Passed Code 1

The reason for it can explain your query of using a period (.) in python which is more or less similar to the usage in other languages.

In Code 1, the name.lower() returns stackoverflow, and then it is again passed through a string method endswith('w') which turns out to be True.

In Code 2, the name.lower() returns stackoverflow same as Code 1 but it is not passed through the endswith('w') method. Instead there is another condition name.endswith('w') which check if name i.e. StackOverFLOW ends with a lower case w which is False and hence, the condition breaks.

Upvotes: 1

Barmar
Barmar

Reputation: 780871

This is called method chaining.

x.method1().method2().method3()

is equivalent to

temp1 = x.method1()
temp2 = temp1.method2()
temp2.method3()

So

if name.lower().endswith('b') and len(name) > 2:

is equivalent to:

lowername = name.lower()
if lowername.endswith('b') and len(name) > 2:

It's not equivalent to

if name.lower() and name.endswith('b') and len(name) > 2:

because name.lower() doesn't modify name. So when you call name.endswith('b'), name still contains the original value, which could be uppercase.

If the value were a mutable type, the method could update it in place and return it. However, the general Python convention is that methods either update in place or they return a new object, they don't do both. That's why list.append() returns None, not the updated list, for instance. (Some functions update in place and then return a related value, e.g. list.pop() removes an element from the list and returns the element.)

Upvotes: 1

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