import re

key=r"<h1>Hello World</h1><h2>Hello error</h3><h2>Hello everyone</h2><h3>Hello everybody</h3><h4>Hello ladies</h4>"

p1=r"(?<=<(h[1-4]>)).+?(?=</\1>)"

pattern1=re.compile(p1)

objs=pattern1.finditer(key)

list=[]

for obj in objs:

    list.append(obj.group())

print (list)

运行结果为[ ]