## Python RegEx – Find numbers of Specific Length in String

To find numbers of specific length, N, is a string, use the regular expression **[0-9]+** to find number strings of any length. **[0-9]** matches a single digit. After you find all the items, filter them with the length specified.

### Example 1: Find numbers of specific length in a string

In the following example, we take a string, and find all the 3 digit numbers in that string.

**Python Program**

```
import re
str = 'We four guys, live at 2nd street of Malibeu 521. I had a cash of $248 in my pocket. I got a ticket with serial number 88796451-52.'
#search using regex
x = re.findall('[0-9]+', str)
print('All Numbers\n',x)
#digits of length N
N=3
def filterNumber(n):
if(len(n)==N):
return True
else:
return False
#filter the list
finalx = list(filter(filterNumber, x))
print('Final List\n',finalx)
```

Run **Output**

```
All Numbers
['2', '521', '248', '88796451', '52']
Final List
['521', '248']
```

**What have we done here?**

Following is the explanation to the notable program statements in the above example.

`re.findall('[0-9]+', str)`

returns all the words that are numbers.- The function
`filterNumber(n)`

returns true if the length of the number`n`

equals length that we specified`N`

. - Filter the list returned in step 1 with the function defined in step 2.
- The filter in step 3 returns the list containing the numbers that are of the length specified.

### Summary

In this tutorial of Python Examples, we learned how to get the list of numbers with a specific length, using Python Regular Expression.

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