How can I remove non-ASCII characters but leave periods and spaces?

You can filter all characters from the string that are not printable using string.printable, like this:

>>> s = "some\x00string. with\x15 funny characters"
>>> import string
>>> printable = set(string.printable)
>>> filter(lambda x: x in printable, s)
'somestring. with funny characters'

string.printable on my machine contains:

0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~ \t\n\r\x0b\x0c

EDIT: On Python 3, filter will return an iterable. The correct way to obtain a string back would be:

''.join(filter(lambda x: x in printable, s))

An easy way to change to a different codec, is by using encode() or decode(). In your case, you want to convert to ASCII and ignore all symbols that are not supported. For example, the Swedish letter å is not an ASCII character:

    >>>s = u'Good bye in Swedish is Hej d\xe5'
    >>>s = s.encode('ascii',errors='ignore')
    >>>print s
    Good bye in Swedish is Hej d

Edit:

Python3: str -> bytes -> str

>>>"Hej då".encode("ascii", errors="ignore").decode()
'hej d'

Python2: unicode -> str -> unicode

>>> u"hej då".encode("ascii", errors="ignore").decode()
u'hej d'

Python2: str -> unicode -> str (decode and encode in reverse order)

>>> "hej d\xe5".decode("ascii", errors="ignore").encode()
'hej d'

According to @artfulrobot, this should be faster than filter and lambda:

import re
re.sub(r'[^\x00-\x7f]',r'', your-non-ascii-string) 

See more examples here Replace non-ASCII characters with a single space

You may use the following code to remove non-English letters:

import re
str = "123456790 ABC#%? .(朱惠英)"
result = re.sub(r'[^\x00-\x7f]',r'', str)
print(result)

This will return

123456790 ABC#%? .()