第六章第2讲:条件与循环(1)
1.python中的缩进,其控制代码块的开始与结束
names = ["Alice","Bela"]
if "Alice" in names:
#print(True) # 如果缩进没有,运行时该行会保错
print(True)
else:
print(False)
2.比较运算符
num1 = int(input("Enter your first number:"))
num2 = int(input("Enter your first number:"))
if num1 < num2:
print(num1,"<",num2)
if num1 > num2:
print(num1,">",num2)
if num1 == num2:
print(num1,"=",num2)
if num1 != num2:
print(num1, "!=", num2)
结果:
Enter your first number:34
Enter your first number:4
34 > 4
34 != 4
3.if-elseif-else
num1 = int(input("Enter your first number:")) if num1 >= 10: print(num1,">=10") elif num1 >= 5: print("5<",num1,"<10") elif num1 >= 1: print("1<",num1,"<5") else: print(num1,"<=0") 结果: Enter your first number:-3 -3 <= 0
4.多条件测试
if的格式:
if条件:
代码块
else:
代码块
# 多条件测试 age = int(input("Enter your age:")) grade = int(input("Enter your grade:")) if age >=18: if grade >= 12: print("You can play this game!") else: print("sorry,you can't play this game!") else: print("sorry,your age <=18! You can't play this game!") # 多条件测试(推荐使用如下方式) age = int(input("Enter your age:")) if age >=18: grade = int(input("Enter your grade:")) if grade >= 12: print("You can play this game!") else: print("sorry,you can't play this game!") else: print("sorry,your age <=18! You can't play this game!")
5. and 、or、not
# and age = int(input("Enter your age:")) grade = int(input("Enter your grade:")) if age >=18 and grade >= 12: print("You can play this game!") else: print("sorry,your age <=18! You can't play this game!") # or age = int(input("Enter your age:")) grade = int(input("Enter your grade:")) if age >=18 or grade >= 12: print("You can play this game!") else: print("sorry,your age <=18! You can't play this game!") # not age = int(input("Enter your age:")) if not(age < 18): grade = int(input("Enter your grade:")) if grade >= 12: print("You can play this game!") else: print("sorry,you can't play this game!") else: print("sorry,your age <=18! You can't play this game!")