For this, you can use the built-in method called startswith(). For example,
mystring = "Morning"
mystring.startswith("Morning") # This line will return true
Also you can use the re module.
import re
regex=re.compile('^Morning')
## regex=re.compile('^Good|^Morning') # used if you have multiple words
mystring="Morning, How are u?"
if re.match(regex, mystring):
print("Yes")