import re

def repl(m):
	res = m[1]
	return res.upper()

content = '''opkpokasdasd
function hui asdasopd
function hui2 aisodad

hui(123)
'''

func = re.findall(r'^function (\w+)', content, flags=re.M)
names = '|'.join(func)
content = re.sub(f'({names})', repl, content)

print(content)