Let's assume we need "clean" strings. Clean means a string should only contain letters `a-z`, `A-Z` and spaces. We assume that there are no double spaces or line breaks.

Write a function that takes a string and returns a string without the unnecessary characters.

### Examples

```python
remove_chars('.tree1')    ==> 'tree'

remove_chars("that's a pie$ce o_f p#ie!")  ==> 'thats a piece of pie'

remove_chars('john.dope@dopington.com')    ==> 'johndopedopingtoncom'

remove_chars('my_list = ["a","b","c"]')    ==> 'mylist  abc'

remove_chars('1 + 1 = 2')    ==> '    ' (string with 4 spaces)

remove_chars("0123456789(.)+,|[]{}=@/~;^$'<>?-!*&:#%_")  ==> '' (empty string)
```

Difficulty: introductory

Starter code:

def remove_chars(s):
	

Solutions:
import re

def remove_chars(s):
    return re.sub(r'[^a-zA-Z ]', '', s)

def remove_chars(s):
    return "".join( c for c in s if c.isalpha() or c==" " )

import re
def remove_chars(s):
    return re.sub(r'[^A-Za-z\s]','',s)

def remove_chars(s):
    return "".join(list(i for i in s if i.isalpha() or i.isspace()))

import re

def remove_chars(s):
    return re.sub(r"[^a-zA-Z\s]", "", s)

def remove_chars(s):
    return ''.join(c for c in s if c.isalpha() or c.isspace())

import re

def remove_chars(s):
    return re.sub('(?i)[^a-z ]', '', s)

import re
def remove_chars(s):
    return re.sub(r'(?i)[^a-z ]', "", s)

def remove_chars(s):
    return ''.join(c for c in s if c.isspace() or c.isalpha())

import re
remove_chars = lambda s: re.sub('[^a-z A-Z]','',s)


import re
remove_chars = lambda s: re.sub('[^a-zA-Z\ ]', '', s)


def remove_chars(s):
    w = ""
    for c in s:
        if c.isalpha() or c == " ":
            w += c
    return w

def remove_chars(s):
    letters = "abcdefghijklmnopqrstuvwxyz "
    return "".join([i for i in s if i in letters or i in letters.upper()])

import re

def remove_chars(s):
    s = re.sub('\W+', ' ', re.sub('[^A-Za-z]+', '', re.sub('[\s]', 'SSSSSSSSSS', s)))
    return re.sub('[S]{10}', ' ', s)

def remove_chars(s):
    for x in s:
            if x != ' ':
                    if not x.isalpha():
                            s = s.replace(x,'')
    return s

import re
def remove_chars(string):
    '''Pattern is anything BUT a-zA-Z and whitespace '''
    pattern = r'[^a-zA-Z\s]'
    newstr = re.sub(pattern, "", string)
    return newstr
    


def remove_chars(s):
    import string
    return ''.join(c for c in s if c == ' ' or c in string.ascii_letters)

import re

def remove_chars(s):
    return re.sub(r"[^a-zA-Z\ ]","",s)

def remove_chars(s):
    import re
    return re.sub('[^a-zA-Z\s]', '', s)

def remove_chars(s):
    # without importing string or re and using a quick logic loop
    ret = ''
    for c in s:
        if c.isalpha() or c is ' ':
            ret += c
    return ret