Return the length of a string array element-wise in Python

To return the length of a string array element-wise, use the numpy.char.str_len() method in Python NumPy. The method returns an output array of integers representing the length of each string element.

Syntax

numpy.char.str_len(a)

Parameters:

• a ? Array-like of str or unicode

Returns: Array of integers representing the length of each string element.

Basic Example

Let's create a simple string array and find the length of each element ?

import numpy as np

# Create array of strings
names = np.array(['Amy', 'Scarlett', 'Katie', 'Brad', 'Tom'])

# Get length of each string element
lengths = np.char.str_len(names)

print("Original array:", names)
print("Lengths:", lengths)

Original array: ['Amy' 'Scarlett' 'Katie' 'Brad' 'Tom']
Lengths: [3 8 5 4 3]

Working with 2D Arrays

The method also works with multi-dimensional string arrays ?

import numpy as np

# Create 2D string array
arr_2d = np.array([['Hello', 'World'], 
                   ['Python', 'NumPy']])

# Get lengths element-wise
lengths = np.char.str_len(arr_2d)

print("2D Array:")
print(arr_2d)
print("\nLengths:")
print(lengths)

2D Array:
[['Hello' 'World']
 ['Python' 'NumPy']]

Lengths:
[[5 5]
 [6 5]]

Detailed Example

Here's a complete example showing array properties and string length calculation ?

import numpy as np

# Create a One-Dimensional array of strings
arr = np.array(['Amy', 'Scarlett', 'Katie', 'Brad', 'Tom'])

# Display array information
print("Array...\n", arr)
print("\nArray datatype...\n", arr.dtype)
print("\nArray Dimensions...\n", arr.ndim)
print("\nOur Array Shape...\n", arr.shape)
print("\nNumber of elements in the Array...\n", arr.size)

# Get string lengths element-wise
print("\nResult (length element-wise)...\n", np.char.str_len(arr))

Array...
 ['Amy' 'Scarlett' 'Katie' 'Brad' 'Tom']

Array datatype...
 <U8

Array Dimensions...
 1

Our Array Shape...
 (5,)

Number of elements in the Array...
 5

Result (length element-wise)...
 [3 8 5 4 3]

Conclusion

The numpy.char.str_len() function efficiently calculates string lengths element-wise for NumPy arrays. It works with both 1D and multi-dimensional string arrays, returning an integer array with corresponding lengths.