Python in keyword is used to check whether a value exists within a given sequence, such as a string, list, tuple, or dictionary.
The basic syntax is as follows:
value in sequence
Here, value represents the element being searched, and sequence is the collection in which the search is performed.
It returns a boolean value, True if the element is found in the sequence, and False otherwise.
Using the ‘in’ Keyword with Strings
Strings are a fundamental data type in Python, and the in keyword is a handy tool for string manipulation.
Let’s consider a simple example:
message = "Hello, World!"
print('Hello' in message)
print('Python' in message)
Output:
True False
In the above example, the in keyword is used to check whether the string Hello and Python exist within the message string.
As expected, Hello is found, resulting in True, while Python is not present, yielding False.
Using the ‘in’ Keyword with Lists, Tuples, and Sets
The in keyword is not limited to just strings; it can also be used with other iterable objects like lists, tuples, and sets.
Let’s explore some examples:
fruits = ['apple', 'banana', 'cherry']
print('banana' in fruits)
print('orange' in fruits)
numbers = (1, 2, 3, 4, 5)
print(3 in numbers)
print(6 in numbers)
colors = {'red', 'green', 'blue'}
print('green' in colors)
print('yellow' in colors)
Output:
True False True False True False
In the above examples, the in keyword is used to check whether specific elements exist within the given lists, tuples, and sets.
If the element is present, the in keyword returns True; otherwise, it returns False.
Using the ‘in’ Keyword with Dictionaries
When it comes to dictionaries, the in keyword checks for the presence of a key rather than a value.
Here’s an example:
student = {'name': 'Alice', 'age': 20, 'grade': 'A'}
print('name' in student)
print('city' in student)
Output:
True False
As shown, the in keyword helps us verify if a key exists in the dictionary.
In this case, name is a key in the student dictionary, returning True, while city is not, resulting in False.
Conclusion
The in keyword is a powerful tool in Python that enables you to check the presence of elements within various data structures such as strings, lists, tuples, sets, and dictionaries.
Whether you’re searching for values, keys, or custom objects, the ‘in’ keyword provides a simple and concise way to perform membership testing.