In the Python programming language, the in operator is membership test operator. You can use it to check if a value exists in an object.
That means you don't need to use a for loop to go through the members and use an if to compare (as you may be used to in C)
So instead of this:
>>> myList = [5,7,8,11,15,17,18,22,26,28,32]
>>> for i in myList:
... if i == 15:
... print("found")
...
found
>>>
You can do this:
>>> myList = [5,7,8,11,15,17,18,22,26,28,32]
>>> if 15 in myList:
... print("found")
...
found
>>>
The in operator can be used on different types of variables like strings, lists, dict, files and more.
In operator
You can see some examples below. The in operator is used to test if its part of the members.
Find if a sub-string is inside a string (is a member) with the in operator:
>>> s = "hello world"
>>> if "world" in s:
... print("found")
...
found
>>>
You can use the in-keyword to find characters (strings of size 1)
>>> s = "hello world"
>>> if "e" in s:
... print("found 'e'")
...
found 'e'
>>>
Lists
A list can be a collection of numbers, strings or other types of data.
The in operator works on all lists, regardless of which data is inside it. You can find a number inside a list with the in operator:
>>> x = [6,2,7,8,3]
>>> if 2 in x:
... print('found')
...
found
>>>
If a list contains strings instead of numbers, no problem, it can find the string.
>>> x = ["Alice","Charlois","Eduard","George","Henry"]
>>> if "Eduard" in x:
... print("Found Eduard")
...
Found Eduard
>>>
Dict
A dictionary is a key-value mapping, this is sometimes named associated array in other programming languages. A dictionary is a bit different.
For a dictionary, the in keyword finds the keys
>>> x = { 'developer':'dev', 'coffee':'cof' }
>>> if 'developer' in x:
... print("found")
...
found
>>>
But not for the values in a dict:
>>> x = { 'developer':'dev', 'coffee':'cof' }
>>> if 'dev' in x:
... print("found")
>>>
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