Python Learning-lambda expressions

Lambda is just an expression, and the function body is much simpler than def. The body of a lambda is an expression, not a block of code. Only a finite amount of logic can be encapsulated in a lambda expression. A lambda expression acts as a function sketch. Allows the definition of a function to be embedded within the code.

#求三个数的和
1Lambda x,y,z:x+y+x2print(f ())    #43 4 Lambda x,y,z:x+y+z5print(f (6))    #

In a normal def function construct, there can be any number of statements, and in the DEF function definition, the first need to give the function a name, for the lambda expression, lambda is an anonymous function, do not need to give a lambda construct any name.

The lambda construct is more convenient, and when you need to construct a lambda function, keep in mind the following points:

1, Lambda is an expression, not a statement, it does not support expression blocks.

2. Lambda is defined where we need it, and it doesn't need to be named.

3. Lambda does not need a return statement

The construction of a lambda with a single parameter

1 # lambda structure construction with a single parameter 2 x = [23,34,55]3Lambda  x:max (x)4print(func (x))   #

Lambda constructs with multiple parameters:

1 # Lambda constructs with multiple parameters 2 price,volume = 60,203Lambda price,volume:price/volume4Print (func (price,volume))   #3.0

Lambda constructs with logical operators

1 # Lambda constructs with logical operators 2 ' SELL ' 3 Lambda  and ' BUY ' 4 Print (func ())    # False

Lambda constructs with conditional expressions

1 # Lambda constructs with conditional expressions 2 Lambda x:'BUY'ifelse'SELL'  3print(func)     #BUY

Building a lambda expression with multiple if...else statements

1 # lambda expression with multiple conditional statements 2 Lambda x:'BUY'ifelse'SELL'  ifelse'None'3print(func (78) )    #SELL

Use a lambda expression with the map, filter, and reduce features

Lambda is typically used in conjunction with functions such as map (), filter (), and reduce ()

1 # Lambda is used with map () mapping functions 2 seq = [1,2,3,4,5]3 func = map (Lambda x:x**2, seq)4Print (List (func))    #[1, 4, 9, +]

1 #Lambda is used with the filter () filter function2Signals = ['Buy','Sell', None,'Sell','Sell','Sell']3Func = Filter (LambdaX:x = ='Buy' orx = ='Sell', signals)4 Print(List (func))#[' Buy ', ' Sell ', ' Sell ', ' Sell ', ' Sell ']

1 # Lambda is used with the reduce () function 2 # In Python 3, the reduce () function has been removed from the global namespace and is now placed in the Fucntools module 3 # If you want to use it, you need to call the reduce () function by introducing the Functools module: 4  from Import Reduce 5 Print (Reduce ((lambda x,y:x + y), [2,1.35,-2.4,3]))   # 3.95

Reference:

1, https://www.quantinsti.com/blog/popular-python-learning-the-lambda-function/

2, 8667176

Python Learning-lambda expressions