how to have re.sub work for multiple pattern replace on list of list?

I have a list of list
input- old_list:

[['hi.','pt','patient','med',...],
['.','md','pt','md',...]...]

my desired output – new_list:

[['hi',' ',' ','medication',...],
[' ', 'medication', ' ',...]...]

and I have tried

1.

adict = {"\.": " ",
        "patient": " ",
        "\bpt\b": " ",
        "\bmed\b":"medication"}

for key, value in adict.items():
    new_list= [[re.sub(key, value, e) for e in d] for d in old_list]

replacements = [('\.', ""),
                ("patient"," "),
                ("\bpt\b", " "),
                ("\bmed\b","medication")]

for old, new in replacements:
    new_list=[]
    new_list= [[re.sub(old, new, e) for e in d] for d in old_list]

3. and replace(new_list, old, new) for ...

but none of them works, the output is the same as the original old_list.
Any suggestions? Thanks!

>Solution :

1. You need to use output of each iteration as input for a next iteration, i.e. in new_list instead of in old_list. And of course to initialize the variable before loop: new_list = old_list.
2. Regex patterns should have r-prefix.
3. As mentioned in comments, avoid naming variables with built-in names like dict and list.

import re

patterns = {
    r"\.": " ",
    r"patient": " ",
    r"\bpt\b": " ",
    r"\bmed\b": "medication",
}
old_list = [['hi.', 'pt', 'patient', 'start med end'], ['.', 'md', 'pt', 'md']]

new_list = old_list
for key, value in patterns.items():
    new_list = [[re.sub(key, value, e) for e in d] for d in new_list]

print(old_list)
print(new_list)