Lambda function

[Uchikago]

Hi, i'm a bit confused with this code

x=10
x=lambda : x+2
print(x())

because the right side of the '=' is evaluated first so this should have returned 12 rather than reported an error as it did
error:

    x=lambda : x+2
TypeError: unsupported operand type(s) for +: 'function' and 'int'

Please explain why this code doesn't work