Python uses lambda functions and list comprehension

Python uses lambda functionsLearning Resources

1. Lambda function Learning
2. List comprehension
3. Multidimensional array Initialization

Lambda functions

• Python supports an interesting syntax that allows you to quickly define the minimum function for a single line. These functions, called Lambda, are borrowed from Lisp and can be used wherever functions are needed.

• def f(x): return x*2, replace with a lambda function can be written as: g = lambda x: x*2` g (3) The result is 6 . (lambda x:x*2) (3) ' is the same effect.

  • This is a lambda function that accomplishes the same thing as the normal function above. Note the short syntax here: there is no parentheses around the argument list, and the return keyword is omitted (implied, because the entire function has only one row). Moreover, the function does not have a function name, but it can be assigned to a variable for invocation
  • You don't even need to assign a value to a variable when you use a lambda function. This may not be the most useful thing in the world, it just shows that the lambda function is just an inline function.
  • In general, a lambda function can receive any number of arguments (including optional parameters) and return the value of a single expression. A lambda function cannot contain commands and cannot contain more than one expression. Do not attempt to cram too much into the lambda function; If you need something more complicated, you should define a normal function, and then you want to make it long enough.我将它们用在需要封装特殊的、非重用代码上，避免令我的代码充斥着大量单行函数。

List derivation (listing comprehension)

• See a simple code

  Testlist = [1,2,3,4]
  def mul2 (x):
  Print x*2
  [Mul2 (i) for I in Testlist]
  [Mul2 (i) for i in Testlist if i%2==0]

Multidimensional array Initialization

multilist = [[0 for col in range(5)] for row in range(3)]

Apply

m = [[ -1.0, 2.0/c-1, -2.0/c+1, 1.0],             [2.0, -3.0/c+1, 3.0/c-2, -1.0],             [ -1.0, 0.0, 1.0, 0.0],             [0.0, 1.0/c, 0.0, 0.0]]multiply = Lambda x:x*cm = [[Multiply (M[col][row]) for Col in Range (4)] for row in range (4)]print [[M[col][row] for Col in range (4)] to row in range (4)]

The work it does: M is a matrix that contains the parameter C, and he calculates the results of the C*m
Thought for a moment, and the last sentence changed to

print [[multiply(each) for each in row] for row in m]

More Pythonic

Python uses lambda functions and list comprehension