条件

if语句

绝对值

def abs2(n):
	if n<0:
		n=-n
	return n

if-else 语句

x=input("x")
x=float(x)
print("hello")
if x<10:
	print("wa")
else:
	print("ro")
print("goodbye")

x=10

hello

ro

goodbye

重新设计abs

def abs(n):
if n>0:
	sign=+1
else:
	sign=-1
return sign*n

if-elif-else

可以用多个elif

def getgrade(score):
	if score>=90:
		grade="A"
	elif score>=80:
		grade="B"
	elif score>=70:
		grade="C"
	elif score>=60:
		grade="D"
	else:
		grade="F"
	

if-else推导式

def abs(n):
	return n if (n>=0) else -n


def abss(n):
	if n>=0:
		return n
	else:
		return -n

print("abs(5)=",abs(5),"and abs(-5)=",abs(-5))

abs(5)=5 and abs(-5)=5

match-case语句

def http_error(ststus):
	match status:
		case 400:
			return "bad request"
		case 404:
			return "not found"
		case 418:
			return "i an a teapot"
		case _:
			return "something is wrong"

练习

def is_graduate(cet4,cet6):
	if cet4>=425:
		if cet6>=425:
			return "yes"
		else:
			return "no"
	else:
		return "no"
	cet4,cet6=input().split()
	
	cet4=float(cet4)
	cet6=float(cet6)
	
	print(is_graduate(cet4,cet6))

改进

def is_graduate(cet4,cet6):
	if cet4>=425 and cet6>=425
		
		return "yes"
		
	else:
		return "no"
	cet4,cet6=input().split()
	
	cet4=float(cet4)
	cet6=float(cet6)
	
	print(is_graduate(cet4,cet6))
	

​

进阶

def is_graduate(cet4,cet6):
	if cet4>=425 and cet6>=425
		
		return "yes"
		
	else:
		return "no"
	cet=input()
	if " " in cet:
		cet4,cet6=input().split()
		cet4=float(cet4)
		cet6=float(cet6)
	else:
		cet4=float(cet)
	    cet6=None
	    
	print(is_graduate(cet4,cet6))
	

	

清晰的代码风格

else部分

b=True

if b:

	print("yes")

else:

	print("no")

空白if部分

b=False
if not b:
	print("no")

用嵌套if 而非and 判断

b1=True

b2=True

if b1 and b2:

	print("both")

用if 而不是else控制

b=True
if b:
	print("yes")
else:
	print("no")

x=10
if x<5:
	print("s")
elif x<10:
	print("m")
elif x<15:
	print("l")
else:
	print("e")

c="a"
if(c>='A') and (c<='z'):
	print('u')
elif(c>='a') and (c<='z'):
	print('l')
else:
	print('n')

使用trick

x=42
if x>0:
	y=99