Active January 31, 2022    /    Viewed 266    /    Comments 0    /    Edit

Example of how to extract first letter of each word in a sentence with python using a regular expression:

Using a python regular expression

Let's consider the following sentence:

````import re`

`s = 'Hello, how are you today'`
```

to extract first letter of each word:

````re.findall(r'\b([a-zA-Z]|\d+)', s)`
```

gives

````['H', 'h', 'a', 'y', 't']`
```

Note that

````l = re.findall(r'\b([a-zA-Z]|\d+)', s)`

`print(type(l) )`
```

returns a list

````<class 'list'>`
```

To convert letters to lower case"

````l = [e.lower() for e in l]`

`print( l )`
```

gives then

````['h', 'h', 'a', 'y', 't']`
```

To join all letters"

````'.'.join(l)`
```

gives

````h.h.a.y.t`
```

Another example with a number in the sentence:

````s = 'Hello, how are you today, 1234'`

`l = re.findall(r'\b([a-zA-Z]|\d+)', s)`
```

to select only letters a solution is to use isalpha():

````l = [e.lower() for e in l if e.isalpha()]`

`print( l )`
```

gives

````['h', 'h', 'a', 'y', 't']`
```

Without using a regular expression

Another solution using only a list comprehension:

````s = 'Hello, how are you today, 1234'`

`l =  [e[0].lower() for e in s.split()]`

`print( [e[0].lower() for e in l if e.isalpha()] )`
```

gives

````['h', 'h', 'a', 'y', 't']`
```

References

Daidalos

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