NumPy strings.partition() – Partition Each String in Array

NumPy strings.partition()

The numpy.strings.partition() function splits each element in an input array at the first occurrence of a specified separator. It returns a 3-tuple containing the part before the separator, the separator itself, and the part after the separator.

Syntax

numpy.strings.partition(a, sep)

Parameters

Parameter	Type	Description
a	array-like	Input array of strings.
sep	array-like	Separator used to split each string element.

Return Value

Returns a 3-tuple of arrays:

1. The first array contains the part before the separator.
2. The second array contains the separator itself.
3. The third array contains the part after the separator.

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Examples

1. Partitioning a Single String

Splitting the string “apple_pie” using the separator “_”.

import numpy as np

# Define an array with a single string
arr = np.array(["apple_pie"])

# Partition the string using "_"
before, sep, after = np.strings.partition(arr, "_")

# Print the results
print("Before separator:", before)
print("Separator:", sep)
print("After separator:", after)

Output:

Before separator: ['apple']
Separator: ['_']
After separator: ['pie']

2. Partitioning an Array of Strings

Splitting multiple fruit names at the first occurrence of “a”.

import numpy as np

# Define an array of fruit names
arr = np.array(["apple", "banana", "cherry", "grape"])

# Partition the strings using "a"
before, sep, after = np.strings.partition(arr, "a")

# Print the results
print("Before separator:", before)
print("Separator:", sep)
print("After separator:", after)

Output:

Before separator: ['' 'b' 'cherry' 'gr']
Separator: ['a' 'a' '' 'a']
After separator: ['pple' 'nana' '' 'pe']

3. Partitioning When the Separator is Not Found

If the separator is not found in a string, the entire string is placed in the first part, and the second and third parts are empty.

import numpy as np

# Define an array with a word that doesn't contain the separator
arr = np.array(["cherry"])

# Partition using "_"
before, sep, after = np.strings.partition(arr, "_")

# Print the results
print("Before separator:", before)
print("Separator:", sep)
print("After separator:", after)

Output:

Before separator: ['cherry']
Separator: ['']
After separator: ['']

4. Partitioning Using a Different Separator

Using a different separator to split strings.

import numpy as np

# Define an array of strings
arr = np.array(["apple-banana", "cherry-mango", "grape-orange"])

# Partition the strings using "-"
before, sep, after = np.strings.partition(arr, "-")

# Print the results
print("Before separator:", before)
print("Separator:", sep)
print("After separator:", after)

Output:

Before separator: ['apple' 'cherry' 'grape']
Separator: ['-' '-' '-']
After separator: ['banana' 'mango' 'orange']

In this case, the separator "-" successfully splits each string into three parts.