CODEWITHSUNDEEP
python
88888
88888

Reputation: 31

Get all chars not in string python

I'm trying to randomly insert characters into a string and I want to be able to strip them out later, so I have to use characters that are not already in the string. I want to use as many characters as possible. How can I get a list of all the characters that are not in the string? I am using Python 2.

Upvotes: 2

Views: 1496

Answers (5)

Moshe
Moshe

Reputation: 9839

The big assumption I'm making here is that you're working with an ASCII string.

Valid characters have integer values between 0 and 255. As such, the following will generate a complete set of all of the valid characters:

all_chars = set(chr(i) for i in range(256))

You can then get the set of characters in your string. That's as easy as running set(mystring).

The difference between those is the subset of what's in all_chars, but not in your string:

unused_chars = all_chars - set(mystring)

So putting that all together:

def get_unused_chars(mystring):
    # Generate the list of every valid ASCII character
    all_chars = set(chr(i) for i in range(256))

    # Determine which characters are unused
    unused_chars = all_chars - set(mystring)

    return unused_chars

Upvotes: 1

Has QUIT--Anony-Mousse
Has QUIT--Anony-Mousse

Reputation: 77454

What is a "letter"?

Assuming ascii:

set(string.ascii_letters) - set(yourstring)

otherwise, define your alphabet appropriately first, then use

set(youralphabet) - set(yourstring)

Upvotes: 2

Francisco Vargas
Francisco Vargas

Reputation: 652

The following should do the trick (given that you want your output string to have a specific size):

from string import letters
from random import choice


def random_letters(not_in, size=1):
    i = 1
    out = []
    while(i <= size):
        char = choice(letters)
        if char.lower() not in not_in:
            out.append(char)
            i += 1
    return ''.join(c for c in out)

print(random_letters('abc', 3))

this outputs a random string without a, b or c of size 3.

Upvotes: 0

Jopela
Jopela

Reputation: 5685

You can use a list comprehension to achieve this:

>>> not_in = 'abcde'                                                                                                       
>>> other_string = 'remove char in'                                                                                        

>>> char_not_in = "".join([c for c in other_string if not c in not_in])                                                    
>>> print(char_not_in)
'rmov hr in'

Upvotes: 0

chepner
chepner

Reputation: 530970

Assuming you have a set of all possible characters:

>>> characters = set('ABCabc')

then it is as simple as

>>> my_str = "abbaAC"
>>> not_in_string = characters - set(my_str)
>>> not_in_string
set(['c', 'B'])

Upvotes: 5

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