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Find the length of each string element in the Numpy array

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NumPy builds on (and is a successor to) the successful Numeric array object. Its goal is to create the corner-stone for a useful environment for scientific computing. NumPy provides two fundamental objects: an N-dimensional array object (ndarray) and a universal function object (ufunc). In this post we are going to discuss ways in which we can find the length of each string element in the given numpy array. Problem #1 : Given a numpy array whose underlying data is of string type. Find the length of each element in the given object. Solution : We are going to use numpy.vectorize() function to find the length of each element in the given numpy array object. 

Python3

# importing the numpy library as np
import numpy as np
 
# Create a numpy array
arr = np.array(['New York', 'Lisbon', 'Beijing', 'Quebec'])
 
# Print the array
print(arr)

                    

Output : Now we will use numpy.vectorize() function to find the length of each element in the given numpy array object. 

Python3

# Use vectorize function of numpy
length_checker = np.vectorize(len)
 
# Find the length of each element
arr_len = length_checker(arr)
 
# Print the length of each element
print(arr_len)

                    

Output : As we can see in the output, we have successfully calculated the length of each string element in the given numpy array object. Problem #2 : Given a numpy array whose underlying data is of string type. Find the length of each element in the given object. Solution : We are going to use List comprehension technique to find the length of each element in the given numpy array object. 

Python3

# importing the numpy library as np
import numpy as np
 
# Create a numpy array
arr = np.array(['New York', 'Lisbon', 'Beijing', 'Quebec'])
 
# Print the array
print(arr)

                    

Output : Now we will use List comprehension technique to find the length of each element in the given numpy array object. 

Python3

# Find the length of each element
arr_len = [len(i) for i in arr]
 
# Print the length of each element
print(arr_len)

                    

Output : As we can see in the output, we have successfully calculated the length of each string element in the given numpy array object.

One additional approach to finding the length of each element in a NumPy array is to use the NumPy function numpy.char.str_len. This function takes a NumPy array of strings as input and returns an array of the lengths of each string. For example:

Python3

import numpy as np
 
# Create a numpy array
arr = np.array(['New York', 'Lisbon', 'Beijing', 'Quebec'])
 
# Find the length of each element
arr_len = np.char.str_len(arr)
 
# Print the length of each element
print(arr_len)
 
#This code is contributed by Edula Vinay Kumar Reddy

                    

This will output: [8 7 7 6] (This code wont work in gfg compiler , install numpy in your local compiler then check )



Last Updated : 02 Jan, 2023
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