我想用Python编写一个函数,根据输入索引的值返回不同的固定值。
在其他语言中,我会使用switch或case语句,但Python似乎没有switch语句。在此场景中,推荐的Python解决方案是什么?
我想用Python编写一个函数,根据输入索引的值返回不同的固定值。
在其他语言中,我会使用switch或case语句,但Python似乎没有switch语句。在此场景中,推荐的Python解决方案是什么?
当前回答
易于记忆:
while True:
try:
x = int(input("Enter a numerical input: "))
except:
print("Invalid input - please enter a Integer!");
if x==1:
print("good");
elif x==2:
print("bad");
elif x==3:
break
else:
print ("terrible");
其他回答
# simple case alternative
some_value = 5.0
# this while loop block simulates a case block
# case
while True:
# case 1
if some_value > 5:
print ('Greater than five')
break
# case 2
if some_value == 5:
print ('Equal to five')
break
# else case 3
print ( 'Must be less than 5')
break
我要把我的两分钱放在这里。Python中没有case/switch语句的原因是因为Python遵循“只有一种正确的方法”的原则。很明显,您可以想出各种方法来重新创建switch/case功能,但实现这一点的Python方法是if/elf构造。即。,
if something:
return "first thing"
elif somethingelse:
return "second thing"
elif yetanotherthing:
return "third thing"
else:
return "default thing"
我只是觉得PEP 8应该在这里获得认可。Python的一个优点是它的简单和优雅。这在很大程度上源于PEP8中提出的原则,包括“只有一种正确的方法可以做某事。”
除了字典方法(我很喜欢,BTW),您还可以使用if elif else来获得switch/case/default功能:
if x == 'a':
# Do the thing
elif x == 'b':
# Do the other thing
if x in 'bc':
# Fall-through by not using elif, but now the default case includes case 'a'!
elif x in 'xyz':
# Do yet another thing
else:
# Do the default
当然,这与switch/case不同——你不可能像放弃break语句那样轻易地通过,但你可以进行更复杂的测试。它的格式比一系列嵌套的if更好,尽管在功能上更接近。
我在谷歌搜索上找不到简单的答案。但我还是想通了。这真的很简单。决定把它贴出来,也许可以防止别人的头上少刮几下。关键是简单的“in”和元组。下面是带有直通的switch语句行为,包括RANDOM直通。
l = ['Dog', 'Cat', 'Bird', 'Bigfoot',
'Dragonfly', 'Snake', 'Bat', 'Loch Ness Monster']
for x in l:
if x in ('Dog', 'Cat'):
x += " has four legs"
elif x in ('Bat', 'Bird', 'Dragonfly'):
x += " has wings."
elif x in ('Snake',):
x += " has a forked tongue."
else:
x += " is a big mystery by default."
print(x)
print()
for x in range(10):
if x in (0, 1):
x = "Values 0 and 1 caught here."
elif x in (2,):
x = "Value 2 caught here."
elif x in (3, 7, 8):
x = "Values 3, 7, 8 caught here."
elif x in (4, 6):
x = "Values 4 and 6 caught here"
else:
x = "Values 5 and 9 caught in default."
print(x)
提供:
Dog has four legs
Cat has four legs
Bird has wings.
Bigfoot is a big mystery by default.
Dragonfly has wings.
Snake has a forked tongue.
Bat has wings.
Loch Ness Monster is a big mystery by default.
Values 0 and 1 caught here.
Values 0 and 1 caught here.
Value 2 caught here.
Values 3, 7, 8 caught here.
Values 4 and 6 caught here
Values 5 and 9 caught in default.
Values 4 and 6 caught here
Values 3, 7, 8 caught here.
Values 3, 7, 8 caught here.
Values 5 and 9 caught in default.
def f(x):
dictionary = {'a':1, 'b':2, 'c':3}
return dictionary.get(x,'Not Found')
##Returns the value for the letter x;returns 'Not Found' if x isn't a key in the dictionary