5 Functions

5.4 Lambda expressions

• Lambda expressions often declare anonymous functions,
  • That is, a small function that is temporarily used without a function name,
  • Temporarily want a function similar to a function but do not want to define a function.
• The key parameter of sorted () and list method sort (),
  • The first parameter of the built-in functions map () and filter ()
• Lambda expressions can only contain one expression, other complex statements are not allowed,
  • But other functions can be called in the expression,
  • The calculation result of this expression is equivalent to the return value of the function.

 

 

• When using lambda expressions, pay attention to the problems that variable scope may bring.
• In the following code, the variable x is defined in the outer scope, and is not a local variable for the lambda expression, so it is wrong.

 

 

• Lambda expression is equivalent to a function with only one return
• The true return value when called depends on the current value of the global variable i.

 

• Lambda expression is very convenient to define some small functions
• If you only need a simple operation, try to use the functions provided in the standard library operator
  • Avoid defining lambda expressions yourself,
  • The functions in operator are more efficient

5.5 Essentials of generator function design