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A Brief Introduction to lambda expressions and pythonlambda expressions in python
Recently, coding found that using lambda still has many advantages. In many cases, the code is more neat and pythonic, so here is a brief summary.
1. What is lambda?
A simple example:
func = lambda
Several advanced syntax concepts of Python (lambda expression closure decorator), pythonlambda
1. Anonymous FunctionsAnonymous function is a function that is not bound to any identifier. It is used in the functional programming ages field. Typical applications:1) passed as a parameter to the high-order
Python Lambda functions and sorting, and pythonlambda
Lambda functions are the smallest function that quickly defines a single row. They are borrowed from Lisp and can be used wherever functions are needed. The following example compares the definition of a traditional function
Python: high-order functions and lambda expressions, pythonlambda
Reason:
The python syntax is simple at a glance, but it is used in NLP. I think it is a bit easy to understand because it is less practical.
Read the source code of youtube_dl and see the usage of the filter () function and the
, 12, 14] reduce (function, sequence, starting_value): calls the function sequentially for the items in sequence, if starting_value exists, it can also be called as an initial value. For example, it can be used to sum the List: >>> def add (x, y): return x + y >>> reduce (add, range (1, 11) 55 (Note: 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10) >>> reduce (add, range (1, 11), 20) 75 (Note: 1 + 2 + 3 + 4 + 5 + 6
There are two ways to define a function in Python, one defined by the normal definition of Def, a function to specify a name, and the second to be defined with a lambda, without specifying a name, called a lambda function.Lambda function
in num: ... new_item = Item + 10 ... New_num.append (new_item) ... >>> >>> print new_num[22, 43, 65, 95]Iv. built-in function filterFilter works by filtering out the conditions in the sequence and then forming a new sequence650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/77/DC/wKioL1Zv4LDiFtx1AABLGudR8bc619.png "title=" Filte.png "alt=" Wkiol1zv4ldiftx1aablgudr8bc619.png "/>>>> NUM1 = [10,9,8,7,6]>>> tmp = filter (
Lambda is an anonymous function, Python lambda can make simple functions concise expression, C + + lambda makes the function similar to nested functions are implementedPython's lambdaLambda[Arg1[,arg2,arg3....argn]]:expression#a
, 6, 8, 10, 12, 14]
Reduce (function, sequence, starting_value): Calls the function sequentially for items in sequence. If starting_value exists, it can also be called as an initial value. For example, it can be used to sum the list:>>> Def add (x, y): Return x + y>>> Reduce (ADD, range (1, 11 ))55 (Note: 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)>>> Reduce (ADD, range (1, 11), 20)75 (Note: 1 + 2 + 3 + 4 + 5 +
Python basic filter, lambda function expression filter (function or None, sequence), where sequence can be list, tuple, string. This function filters out all elements in the sequence that return True or bool (return value) as True when calling the
Lambda
Lambda is used to compile simple functions.
Lambda is used as follows: lambda arg1, arg2, arg3,..., argn: expression
Fs = [(lambda n, I = I: I + n) for I in range (10)]>>> Fs [3] (4)7>>> Fs [4] (4)8>>> Fs [5] (4)9
Filter
Filter, map, and reduce are all
This article mainly introduces the special syntax in Python: filter, map, reduce, and lambda. This article provides code examples for this special syntax. For more information, see
Filter (function, sequence ):Execute function (item) in sequence for items in sequence, and combine items with the execution result of True
A lambda function is also called an anonymous function, that is, the function does not have a specific name. Let's look at an example:def f (x): Return x**2print F (4)The use of lambda in Python is written like this:g =
Common methods for modules and modules
Function-Type programming
Yield
Ternary operations
Lambda expression
Built-in Culvert number
Common modules
"Common methods for modules and modules"The critical __init__.py #包一定要有这个__init__. py file, he is the package, in order to use the form Package name Import module name (. py file name) to refer to a module of this package
;> round (1.12, 1)
1.1
>>> round (1.123, 2)
1.12
The first argument is a floating-point number, and the second argument is a reserved scale, optional, and left to an integer by default if not written.If there is a requirement for precision after interception, join the following link:
A little pit in Python about the round functionWhy does Python not solve rounded (round) "Bugs"?
Data Filtering (filter)
Use
Lambda expressionanonymous functionsThe-LAMDBA function is a minimal function that quickly defines a single line, borrowed from Lisp, and can be used wherever a function is needed.Example:Function:>>> def fun (x, y): ... return x*y >>> fun (23,2) LambdaLambda X,y:x*y#lambda
Use Lambda in Python to create anonymous functions. Lambda comes from the lisp language. The Lambda format is as follows:
Lambda arg1, arg2....: Lambda creates a function object, but do
map function:
Prototype: Map (function, sequence), which is to map a list to another list,
How to use:
def f (x):
Return x**2
L = Range (1,10)
Map (f,l)
OUT[3]: [1, 4, 9, +, BA] reduce function
Prototypes: Reduce (function, sequence, startvalue), which is to generalize a list into one output,How to use:
def f2 (x,y):
This article mainly introduces the comparison between Lambda and def usage in Python, and analyzes the difference between Lambda and def and the use of it, which has a certain reference value, and the need for friends can refer to
This paper compares and analyzes the usage of lambda and def in
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