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NumPy: Add two zeros to the beginning of each element of a given array of string values

NumPy String: Exercise-19 with Solution

Write a NumPy program to add two zeros to the beginning of each element of a given array of string values.

Sample Solution:

Python Code:

import numpy as np 

nums = np.array(['1.12', '2.23', '3.71', '4.23', '5.11'], dtype=np.str)
print("Original array:")
print(nums)
print("\nAdd two zeros to the beginning of each element of the said array:")
print(np.char.add('00', nums))
print("\nAlternate method:")
print(np.char.rjust(nums, 6, fillchar='0'))

Sample Output:

Original array:
['1.12' '2.23' '3.71' '4.23' '5.11']

Add two zeros to the beginning of each element of the said array:
['001.12' '002.23' '003.71' '004.23' '005.11']

Alternate method:
['001.12' '002.23' '003.71' '004.23' '005.11']

Python Code Editor:

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Python: Tips of the Day

Getting the last element of a list:

some_list[-1] is the shortest and most Pythonic.

In fact, you can do much more with this syntax. The some_list[-n] syntax gets the nth-to-last element. So some_list[-1] gets the last element, some_list[-2] gets the second to last, etc, all the way down to some_list[-len(some_list)], which gives you the first element.

You can also set list elements in this way. For instance:

>>> some_list = [1, 2, 3]
>>> some_list[-1] = 5 # Set the last element
>>> some_list[-2] = 3 # Set the second to last element
>>> some_list
[1, 3, 5]

Note that getting a list item by index will raise an IndexError if the expected item doesn't exist. This means that some_list[-1] will raise an exception if some_list is empty, because an empty list can't have a last element.

Ref: https://bit.ly/3d8TfFP