Supplementary operation
1.in and not in # judge whether something in there
content = input "Please enter the text:"
if "sex" in content:
print ( "contains sensitive character")
while True:
content = input "Please enter the text:"
if "sex" in content:
print ( "contains sensitive character")
else:
print(content)
break
2. Priority
not 2>1
Interpretation: not 2> 1 # error
not 2> 1 # is correct not and or symbols of all operations in the minimum level of