NumPy - String Functions

The NumPy package contains a number of functions which can be used on an array with dtype string. Below mentioned are most commonly used functions for this purpose:

Lets discuss these functions in detail:

numpy.char.add() function

The numpy.char.add() function returns element-wise string concatenation for two arrays of string or Unicode.

import numpy as np
Arr1 = np.array(["Hello", "Hi"])
Arr2 = np.array([" World", " Python"])

print(np.char.add(Arr1, Arr2))
print(np.char.add("Python", " Programming"))

The output of the above code will be:

['Hello World' 'Hi Python']
Python Programming

numpy.char.multiply() function

The numpy.char.multiply() function returns the string with multiple concatenation, element-wise.

import numpy as np
Arr = np.array(["Hello", "Hi"])

print(np.char.multiply(Arr, 2))
print(np.char.multiply("Hi", 3))

The output of the above code will be:

['HelloHello' 'HiHi']
HiHiHi

numpy.char.center() function

The numpy.char.center() function returns a copy of the string with elements centered in the string of specified length.

import numpy as np
Arr = np.array(["Learn", "Python"])

#padding the string from both side with *
#to make the length of string as 10
print(np.char.center(Arr, 10, "*"))
print(np.char.center("Hi", 10, "*"))

The output of the above code will be:

['**Learn***' '**Python**']
****Hi****

numpy.char.capitalize() function

The numpy.char.capitalize() function returns a copy of the string with only the first character capitalized.

import numpy as np
Arr = np.array(["learn", "python"])

print(np.char.capitalize(Arr))
print(np.char.capitalize("hi"))

The output of the above code will be:

['Learn' 'Python']
Hi

numpy.char.title() function

The numpy.char.title() function returns a copy of the string with the element-wise title cased version of the string or Unicode.

import numpy as np
Arr = np.array(["learn python", "hello world"])

print(np.char.title(Arr))
print(np.char.title("hi john"))

The output of the above code will be:

['Learn Python' 'Hello World']
Hi John

numpy.char.lower() function

The numpy.char.lower() function returns a copy of the string with the elements converted to lowercase.

import numpy as np
Arr = np.array(["lEArn", "pyTHon"])

print(np.char.lower(Arr))
print(np.char.lower("HeLLo"))

The output of the above code will be:

['learn' 'python']
hello

numpy.char.upper() function

The numpy.char.upper() function returns a copy of the string with the elements converted to uppercase.

import numpy as np
Arr = np.array(["lEArn", "pyTHon"])

print(np.char.upper(Arr))
print(np.char.upper("HeLLo"))

The output of the above code will be:

['LEARN' 'PYTHON']
HELLO

numpy.char.split() function

The numpy.char.split() function returns a list of words in the string.

import numpy as np
Arr = np.array(["Learn Python", "Hello", "World"])

print(np.char.split(Arr))
print(np.char.split("Hi John"))

The output of the above code will be:

[list(['Learn', 'Python']) list(['Hello']) list(['World'])]
['Hi', 'John']

numpy.char.splitlines() function

The numpy.char.splitlines() function returns a list of lines in the string, breaking at line boundaries.

import numpy as np
Arr = np.array(["Programming\nis\nfun", "Python", "Hi\nJohn"])

print(np.char.splitlines(Arr))
print(np.char.splitlines("Hi\nJohn"))

The output of the above code will be:

[list(['Programming', 'is', 'fun']) list(['Python']) list(['Hi', 'John'])]
['Hi', 'John']

numpy.char.strip() function

The numpy.char.strip() function returns a copy of the string with the leading and trailing white spaces removed.

import numpy as np
Arr = np.array(["Hello World  ", " Python "])

print(np.char.strip(Arr))
print(np.char.strip("  Hi John  "))

The output of the above code will be:

['Hello World' 'Python']
Hi John

numpy.char.join() function

The numpy.char.join() function returns a string which is the concatenation of the strings in the sequence.

import numpy as np
Arr = np.array(["Hi", "Hello"])

print(np.char.join(":", Arr))
print(np.char.join(":", "HMS"))

The output of the above code will be:

['H:i' 'H:e:l:l:o']
H:M:S

numpy.char.replace() function

The numpy.char.join() function returns a copy of the string with all occurrences of substring replaced by the new string.

import numpy as np
Arr = np.array(["Hello", "World"])

#replacing "World" with "Python" in Arr
print(np.char.replace(Arr, "World", "Python"))

#replacing "Hi" with "Hello" in given string
print(np.char.replace("Hi john", "Hi", "Hello"))

The output of the above code will be:

['Hello' 'Python']
Hello john

numpy.char.decode() and numpy.char.encode() function

The numpy.char.decode() function is used to decode the specified string element-wise using the specified codec, whereas numpy.char.encode() function is used to encode the decoded string element-wise.

import numpy as np
Arr = np.array(["Hello", "World"])

#encoding Arr
enstr = np.char.encode(Arr, 'cp500')
#decoding encoded Arr
destr = np.char.decode(enstr, 'cp500')

print("encoded string:", enstr)
print("decoded string:", destr)

The output of the above code will be:

encoded string: [b'\xc8\x85\x93\x93\x96' b'\xe6\x96\x99\x93\x84']
decoded string: ['Hello' 'World']