Numpy Isnumeric Function: Mastering Numeric String Validation
Tags: numpy, coding, programming, tutorial
Published: 2024-06-30 03:24:33


## Introduction

In this lab, we will cover the `isnumeric()` function of the **char module** in the Numpy library. This function is used to check if a string contains only numeric characters. The function returns **True** if there are only numeric characters in the string, otherwise, it returns **False**.

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## Import Numpy Library

We need to import the numpy library before we can use the `isnumeric()` function. We use the `import` keyword followed by the library name `numpy` and the nickname `np`:

```python
import numpy as np
```


## Using `isnumeric()` with a Single String

We can use the `isnumeric()` function to check if a single string contains only numeric characters. Let's use an example string `"12Apple90"` and apply the `isnumeric()` function to it:

```python
import numpy as np

string1 = "12Apple90"
print("The Input string is:")
print(string1)

x = np.char.isnumeric(string1)
print("The Output is:")
print(x)
```

Output:

```python
The Input string is:
12Apple90
The Output is:
False
```

As we can see, the `isnumeric()` function returns **False** as there are non-numeric characters in the input string.


## Using `isnumeric()` with an Array

We can also use the `isnumeric()` function with an array of strings. Let's use an example array `inp_ar` which contains a mixture of numeric and non-numeric strings:

```python
import numpy as np

inp_ar = np.array(['1', '2000', '90', '3.5', '0'])
print("The Input array is:")
print(inp_ar)

outp_arr = np.char.isnumeric(inp_ar)
print("The Output array is:")
print(outp_arr)
```

Output:

```python
The Input array is:
['1' '2000' '90' '3.5' '0']
The Output array is:
[ True  True  True False  True]
```

As we can see, the `isnumeric()` function returns an array of boolean values with **True** indicating that the string contains only numeric characters and **False** indicating that the string contains non-numeric characters.


## Limitations of `isnumeric()`

It is important to note that the `isnumeric()` function returns **False** for a string with a numeric value with a decimal, as shown in Example 2 above.


## Summary

In this lab, we learned about the `isnumeric()` function of the Numpy library. We covered how to use it with single strings and arrays, as well as the limitations of the function.

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