NumPy strings.isdecimal()

The numpy.strings.isdecimal() function checks if each element in an input array consists only of decimal characters. It returns a boolean array where each element is True if the corresponding input element contains only decimal characters and False otherwise.

Syntax

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numpy.strings.isdecimal(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True)

Parameters

Parameter	Type	Description
`x`	array_like (StringDType or str_ dtype)	Input array of strings to be checked for decimal characters.
`out`	ndarray, None, or tuple of ndarray and None, optional	Optional output array to store the result. If None, a new array is created.
`where`	array_like, optional	Boolean mask that specifies which elements to check. Elements where `where=False` retain their original value.
`casting`	str, optional	Defines the casting behavior when performing the operation.
`order`	str, optional	Memory layout order of the output array.
`dtype`	data-type, optional	Specifies the data type of the output array.
`subok`	bool, optional	Determines if subclasses of ndarray are preserved in the output.

Return Value

Returns an array of boolean values indicating whether each input string contains only decimal characters. If the input is a scalar, a single boolean value is returned.

Examples

1. Checking Decimal Characters in a Single String

Here, we check whether a single string consists entirely of decimal characters.

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import numpy as np

# Define a string
string_value = np.str_("12345")

# Check if the string contains only decimal characters
result = np.strings.isdecimal(string_value)

# Print the result
print("Is '12345' decimal?:", result)

Output:

Is '12345' decimal?: True

2. Checking Decimal Characters in an Array of Strings

We apply isdecimal() to an array of strings to check which elements contain only decimal characters.

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import numpy as np

# Define an array of strings
string_array = np.array(["123", "45.6", "789", "abcd", "١٢٣"], dtype="str")

# Check which strings contain only decimal characters
decimal_check = np.strings.isdecimal(string_array)

# Print the results
print("Input Strings:", string_array)
print("Is Decimal:", decimal_check)

Output:

Input Strings: ['123' '45.6' '789' 'abcd' '١٢٣']
Is Decimal: [ True False  True False  True]

3. Using the `out` Parameter

Storing results in an output array instead of creating a new one.

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import numpy as np

# Define an array of strings
string_array = np.array(["123", "text", "456", "7.89"], dtype="str")

# Create an output array
output_array = np.empty_like(string_array, dtype=bool)

# Check decimal characters and store result in output_array
np.strings.isdecimal(string_array, out=output_array)

# Print the results
print("Output array:", output_array)

Output:

Output array: [ True False  True False]

4. Using the `where` Parameter

Using a condition to check decimal characters only for selected elements.

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import numpy as np

# Define an array of strings
string_array = np.array(["123", "abc", "987", "45.6"], dtype="str")

# Define a mask (check decimal only where mask is True)
mask = np.array([True, False, True, False])

# Apply isdecimal() where mask is True
result = np.strings.isdecimal(string_array, where=mask)

# Print the results
print("Result with mask:", result)

Output:

Result with mask: [ True False  True False]

The function checks only elements where mask=True. The other values remain unchanged.

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NumPy strings.isdecimal() – Check if Each Element Contains Only Decimal Characters