Replace specific expression in python

I want to replace a string contains "${}" with "*" in python.
example, replace:

"This is ${ali} from team"

with

"This is * from team"

I’ve tried this but does not work:

re.sub("^$.*}$", "*",str)

>Solution :

import re
s = "This is ${ali} from team ${asda} "

s = re.sub(r'\${.[^}]+}','*',s)
print(s)

OUTPUT

This is * from team *

Pythonic way

s = "This is ${ali} from team ${asd}"

s = list(s)
try:
    while '$' in s and '}' in s:
        s[s.index('$'):s.index('}')+1] = '*'
except ValueError:
    pass
s = ''.join(s)
print(s) # → This is * from team *