NumPy - String Functions

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String functions in NumPy are designed to operate on arrays of strings. They are part of the NumPy char module, which provides a set of vectorized string operations that can be applied to each element of a string array.

Key Features of NumPy String Functions

Following are the key features of NumPy String Functions −

• Element-wise Operations: The core advantage of NumPy string functions is their ability to perform operations on each element of an array independently. This allows for efficient manipulation of large datasets.
• Vectorization: By using NumPy library operations are vectorized i.e., which enhances performance compared to traditional Python string handling methods. Vectorization utilizes optimized C libraries to perform computations by reducing the execution time significantly.
• Compatibility with Arrays: NumPy string functions work directly with arrays of strings by making it easier to process large amounts of textual data without needing to convert them into lists or other formats.

The String operations are performed element-wise on arrays. They are particularly useful for low-level data manipulation and efficient computation.

List of String Functions

The following functions are used to perform vectorized string operations for arrays of dtype numpy.string_ or numpy.unicode_. They are based on the standard string functions in Python's built-in library.

Let's look at the important functions quickly −

The add() Function

The add() function in NumPy is used to concatenate strings using the + operator as shown in the example below −

a = "Hello"
b = "World"
result = a + " " + b
print(result)

Following is the output obtained −

Hello World

The multiply() Function

The multiply() function in NumPy is used to multiply(repeat) strings using the * operator as shown in the example below −

a = "Hello"
result = a * 3
print(result)

This will produce the following result −

HelloHelloHello

The center() Function

The center() function centers a string in a field of a specified width, padding it with spaces or a specified character −

s = "hello"
result = s.center(10, '*')
print(result)

Following is the output of the above code −

**hello***

The capitalize() Function

The capitalize() function capitalizes the first character of the string and makes all other characters lowercase −

s = "hello world"
result = s.capitalize()
print(result)

The output obtained is as shown below −

Hello world

The title() Function

The title() function capitalizes the first letter of each word in the string −

s = "hello world"
result = s.title()
print(result)

After executing the above code, we get the following output −

Hello World

The lower() and upper() Functions

The lower() function converts all characters in the string to lowercase. Whereas, the upper() function converts all characters in the string to uppercase −

s = "Hello World"
res1 = s.lower()
res2 = s.upper()
print("Lowercase:", res1)
print("Uppercase:",res2)

The result produced is as follows −

Lowercase: hello world
Uppercase: HELLO WORLD

The decode() Function

In Python 3, the decode() function is typically used for byte objects, not strings. To decode bytes to a string, you use the decode() function −

# Bytes object
b = b"hello world"
result = b.decode('utf-8')
print(result)

We get the output as shown below −

hello world