# How to Split a String Between Numbers and Letters?

Problem Formulation: Given a string of letters and numbers. How to split the string into substrings of either letters or numbers by using the boundary between a letter and a number and vice versa.

Examples: Have a look at the following examples of what you want to accomplish.

````'111A222B333C'     --->    ['111', 'A', '222', 'B', '333', 'C']`
`'Finxter42'        --->    ['Finxter', '42']`
`'Hello world'     --->    ['Hello', ' world']````

## Method 1: re.split()

The `re.split(pattern, string)` method matches all occurrences of the `pattern` in the `string` and divides the string along the matches resulting in a list of strings between the matches. For example, `re.split('a', 'bbabbbab')` results in the list of strings `['bb', 'bbb', 'b']`.

```# Method 1: re.split()
import re
s = '111A222B333C'
res = re.split('(\d+)', s)
print(res)
# ['', '111', 'A', '222', 'B', '333', ' C']```

The `\d` special character matches any digit between 0 and 9. By using the maximal number of digits as a delimiter, you split along the digit-word boundary. Note that you don’t consume the split character by wrapping it into a matching group using the parentheses `(...)`. If you leave out the parentheses, it’ll consume the numbers and the result wouldn’t contain any consecutive numbers.

## Method 2: re.findall()

The `re.findall(pattern, string)` method scans `string` from left to right, searching for all non-overlapping matches of the `pattern`. It returns a list of strings in the matching order when scanning the string from left to right.

```# Method 2: re.findall()
import re
s = '111A222B333C'

res = re.findall('(\d+|[A-Za-z]+)', s)

print(res)
# ['111', 'A', '222', 'B', '333', 'C']```

## Method 3: itertools.groupby()

```# Method 3: itertools.groupby()
from itertools import groupby
s = '111A222B333C'

res = [''.join(g) for _, g in groupby(s, str.isalpha)]
print(res)
# ['111', 'A', '222', 'B', '333', 'C']```
• The `itertools.groupby(iterable, key=None)` function creates an iterator that returns tuples `(key, group-iterator)` grouped by each value of `key`. We use the `str.isalpha()` function as key function.
• The `str.isalpha()` function returns `True` if the string consists only of alphabetic characters.

## Programmer Humor

There are only 10 kinds of people in this world: those who know binary and those who don’t.
👩🧔‍♂️
~~~

There are 10 types of people in the world. Those who understand trinary, those who don’t, and those who mistake it for binary.

👩🧔‍♂️👱‍♀️

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