in pyhton regex ?<= means code example

Example 1: python regular expression

import re

# The string you want to find a pattern within
test_string = 'Hello greppers!'

# Creating a regular expression pattern
# This is a simple one which finds "Hello"
pattern = re.compile(r'Hello')

# This locates and returns all the occurences of the pattern
# within the test_string
match = pattern.finditer(test_string)

# Outputs all the ocurrences which were returned as 
# as match objects
for match in matches:
  print(match)

Example 2: regex in python

# pip install regex
import re
# simple find all
sample = "Nothing lasts... but nothing is lost"
found = re.findall("thing", sample)
print(found)