Using regular expressions – documentation for further reference
import re
text="gfgfdAAA1234ZZZuijjk"
m = re.search('AAA(.+?)ZZZ', text)
if m:
found = m.group(1)
# found: 1234
or:
import re
text="gfgfdAAA1234ZZZuijjk"
try:
found = re.search('AAA(.+?)ZZZ', text).group(1)
except AttributeError:
# AAA, ZZZ not found in the original string
found = '' # apply your error handling
# found: 1234