NumPy String Functions

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

These functions are defined in the character array class (numpy.char).

numpy.char.add()

The numpy.char.add() function concatenates elements of two arrays sequentially.

Example

import numpy as np 

print('Concatenating two strings:')
print(np.char.add(['hello'], [' xyz']))
print('\n')

print('Concatenation example:')
print(np.char.add(['hello', 'hi'], [' abc', ' xyz']))

Output:

Concatenating two strings:
['hello xyz']

Concatenation example:
['hello abc' 'hi xyz']

numpy.char.multiply()

The numpy.char.multiply() function performs multiple concatenations.

Example

import numpy as np 

print(np.char.multiply('tutorialpro ', 3))

Output:

tutorialpro tutorialpro tutorialpro

numpy.char.center()

The numpy.char.center() function centers the string and pads it with specified characters on the left and right.

Example

import numpy as np 

# np.char.center(str, width, fillchar)
# str: string, width: length, fillchar: padding character
print(np.char.center('tutorialpro', 20, fillchar='*'))

Output:

*******tutorialpro*******

numpy.char.capitalize()

The numpy.char.capitalize() function converts the first character of the string to uppercase.

Example

import numpy as np 

print(np.char.capitalize('tutorialpro'))

Output:

tutorialpro

numpy.char.title()

The numpy.char.title() function converts the first character of each word in the string to uppercase.

Example

import numpy as np

print(np.char.title('i like tutorialpro'))

Output:

I Like tutorialpro

numpy.char.lower()

The numpy.char.lower() function converts each element of the array to lowercase. It calls str.lower on each element.

Example

import numpy as np 

# Operating on array
print(np.char.lower(['tutorialpro', 'GOOGLE']))

# Operating on string
print(np.char.lower('tutorialpro'))

Output:

['tutorialpro' 'google']
tutorialpro

numpy.char.upper()

The numpy.char.upper() function converts each element of the array to uppercase. It calls str.upper on each element.

Example

import numpy as np 

# Operating on array
print(np.char.upper(['tutorialpro', 'google']))

Output:

['TUTORIALPRO' 'GOOGLE']

print(np.char.upper(['tutorialpro', 'google']))

# Operating on strings
print(np.char.upper('tutorialpro'))

Output result:

['TUTORIALPRO' 'GOOGLE'] TUTORIALPRO

### numpy.char.split()

numpy.char.split() splits the string by the specified delimiter and returns an array. By default, the delimiter is a space.

## Example

```python
import numpy as np

# Default delimiter is a space
print(np.char.split('i like tutorialpro?'))
# Delimiter is .
print(np.char.split('www.tutorialpro.org', sep='.'))

Output result:

['i', 'like', 'tutorialpro?']
['www', 'tutorialpro', 'org']

numpy.char.splitlines()

numpy.char.splitlines() splits the string by newline characters and returns an array.

Example

import numpy as np

# Newline character \n
print(np.char.splitlines('i\nlike tutorialpro?'))
print(np.char.splitlines('i\rlike tutorialpro?'))

Output result:

['i', 'like tutorialpro?']
['i', 'like tutorialpro?']

\n, \r, \r\n can all be used as newline characters.

numpy.char.strip()

numpy.char.strip() removes specific characters from the beginning or end.

Example

import numpy as np

# Remove 'a' characters from the beginning and end of the string
print(np.char.strip('ashok tutorialproa', 'a'))

# Remove 'a' characters from the beginning and end of array elements
print(np.char.strip(['atutorialproa', 'admin', 'java'], 'a'))

Output result:

shok tutorialpro
['tutorialpro' 'dmin' 'jav']

numpy.char.join()

numpy.char.join() joins elements or strings in an array with a specified delimiter.

Example

import numpy as np

# Operate on strings
print(np.char.join(':', 'tutorialpro'))

# Specify multiple delimiters for array elements
print(np.char.join([':', '-'], ['tutorialpro', 'google']))

Output result:

t:u:t:o:r:i:a:l:p:r:o
['t:u:t:o:r:i:a:l:p:r:o' 'g-o-o-g-l-e']

numpy.char.replace()

numpy.char.replace() replaces all occurrences of a substring with a new string.

Example

import numpy as np

print(np.char.replace('i like tutorialpro', 'oo', 'cc'))

Output result:

i like tutilcpro

numpy.char.encode()

numpy.char.encode() calls str.encode on each element of the array. The default encoding is utf-8, and standard Python codecs can be used.

Example

import numpy as np

a = np.char.encode('tutorialpro', 'cp500')
print(a)

Output result:

b'\x99\xa4\x95\x96\x96\x82'

numpy.char.decode()

numpy.char.decode() decodes the encoded elements using str.decode().

Example

import numpy as np

a = np.char.encode('tutorialpro', 'cp500')
print(a)
print(np.char.decode(a, 'cp500'))

Output result:

b'\x99\xa4\x95\x96\x96\x82'
tutorialpro