条件语句：
1.if...else...;
2.if...elif...esle
举例：
1.if...else...
“age_of_princal = 56
guess_age = int(input(">>>>:"))
if guess_age == age_of_princal:
print("Yes,you got it")
else:
print("No,it's wrong.")”
2.if...elif...esle...
"score = int(input("score:"))
if score > 90:
print("A")
elif score > 80:
print("B")
elif score > 70:
print("C")
elif score > 50:
print("D")
else:
print("加油")"