Lambda而不是"if"语句

Question

我听说可以if用lambda 替换一个语句.

这在Python中可行吗？如果是这样,怎么样？

Answer 1

也许你指的是这样的东西(Lambda演算)？

If = lambda test, x, y: test(x, y)
True = lambda x, y: x
False = lambda x, y: y

哪个你可以用...

# I guess you have to convert them sometimes... oh well
C = lambda b: [False, True][b]

x = If(C(2 > 3), "Greater", "Less")
print(x)
# "Less"

但现在事情开始分崩离析了......

If(C(2 > 3), print("Greater"), print("Less"))
# Invalid syntax unless you use
    #     from __future__ import print_function
# And if you do, it prints both!
# (Because python has eager evaluation)

# So we could do
True = lambda x, y: x()
False = lambda x, y: y()

# And then
If(C(2 > 3), lambda:print("Greater"), lambda:print("Less"))
# "Less"

所以,不那么漂亮或有用.但它的确有效.