我想从一个 lambda 返回两个值并分配给另一个，但我得到了错误

Question

I had tried to return values to a and b by using the below method

(lambda a,b:print(a,b))((lambda x:(x,[int(i)**len(x) for i in x]))('153'))

but this shows error,i need some help to fix this.

TypeError: <lambda>() missing 1 required positional argument: 'b'

Answer 1

The inner function returns a single tuple of two values, but the outer function expects two separate values. Use * -unpacking to have each value of the tuple passed as a separate parameter:

#       v takes two parameters     v provides one tuple of two values
(lambda a,b:print(a,b))(*(lambda x:(x,[int(i)**len(x) for i in x]))('153'))
#                       ^ unpack operator

Note that print already takes positional arguments – (lambda a,b:print(a,b)) can be replaced by just print . Also, Python3.8 introduces the := assignment operator, which can often be used instead of a lambda to emulate let expressions. This shortens the expression significantly:

# v print takes multiple arguments
print(*(x := '153', [int(i)**len(x) for i in x]))
#         ^ assignment operator binds in current scope

Answer 2

@MisterMiyagi posted the correct answer using the given structure. However, I can't think of a case where using two lambdas in the way you did would be useful. Defining a function would make the code much more readable:

def print_values(string):
    values = [int(i)**len(string) for i in string]
    print(string, values)

print_values("153")

Or if you want it shorter:

def print_values(string):
    print(string, [int(i)**len(string) for i in string])

print_values("153")