findall only works with a string as input not a list.

You probably want to use map and re.match or re.search for example:

Also your regex has multiple repeat symbols in it and needs some tuning, this one seems to work J\w{3}son

import re
a = ["Jackson", "Johnson", "Jason"]
c = list(map(lambda x: re.search("J\w{3}son",x), a))
print([i.string for i in c if i])

output:

['Jackson', 'Johnson']

Update if your input type is just a string then your original expression was fine you just need to change the regex to the example above

import re
a = "Jackson Johnson Jason"
b = re.findall("J\w{3}son", a)
print(b)

output:

['Jackson', 'Johnson']

Your goal is to split a string into tokens by a separator, so a better way to do this than with re.findall() is with re.split(). In this case, you can use

>>> re.split(r"[,;.]\s", s)
['this', 'that', 'talk', 'love', 'hate', 'good', 'bad', 'all good.']

Unfortunately, this method either puts the period at the end of the last item if you use [,;.]\s as the regular expression, and adds an empty string at the end of the result list if you instead use [,;.]\s? as the regular expression. We can deal with this, however, by removing the last string:

>>> re.split(r"[,;.]\s?", s)[:-1]
['this', 'that', 'talk', 'love', 'hate', 'good', 'bad', 'all good']

This solution should work:

me = re.findall(rf"(?<='(.+)'+{variable}+'(.+)')(.*?)(?='(.+)+{variable}+(.+)')", raw)

You also can add many different variables as you wish. Add rf for the regular expression and the desired variables in between {}

import re

text = "regex is the best"    
var1 = "is the"
var2 = "best"
yes = re.findall(rf"regex {var1} {var2}", text)

print(yes)

['regex is the best']