Recommended articles about php eval() function

Suppose there is a dictionary in python as follows: x={'a':'1,2,3', 'b':'2,3,4'} needs to be merged into: x={'c':' 1,2,3,4'} needs to do three things: 1. Convert the string into a numerical list 2. Merge the two lists and add new key values ​​3. Remove duplicate elements Step 1 through the commonly used function eval () can be done. In the second step, you need to add a key value and add elements. In the third step, you can use the properties of the set collection to achieve the effect of deduplication, but in the end you need to convert the set collection into a list list. The code is as follows: x={'a':'1,2,3','b':'2,3,4'} x['c']=list(set(eval(x['a'])+eval(x['b']))) del x['a']

1. Example code for merging dictionary key values ​​and removing duplicate elements using Python

Introduction: Suppose there is a dictionary in python as follows: x={'a':'1,2,3', 'b':'2,3,4' }Needs to be merged into: x={'c':'1,2,3,4'} Three things need to be done: 1. Convert the string into a numerical list 2. Merge the two lists and add new key values 3. To remove duplicate elements, the first step can be done through the commonly used function eval(). The second step needs to add a key value and add elements. The third step uses the properties of the set collection

2. JavaScript cheats lexical eval, with and catch and their performance issues

## Introduction: Normally, the scope chain of the execution context will not change, so many students think that there is only lexical scope (static scope) in JavaScript. The scope is determined by the function declaration position when writing the code. But in fact, there are several The mechanism can deceive the lexical. They are with(), eval() and the catch statement of the try-catch statement. Among them, we should not use with and eval (it will cause many problems). Deceiving the lexical means deceiving the lexical scope, that is, Say, modify the scope chain at runtime

3. The setTimeout secret that JavaScript developers should know

Introduction: The timer setTimeout is something we often use. It is used to call a function or calculate an expression after a specified number of milliseconds. Syntax: setTimeout(code, millisec, args); Note: If code is a string, it is equivalent to executing the eval() method to execute the code. Of course, this article not only tells you how to use setTimeout, but also understands how it is executed. 1. Let’s look at the principle of setTimeout first

4. Three methods of parsing JSON data in JavaScript

Introduction: This article mainly introduces three methods of parsing JSON data in JavaScript. This article explains the eval() method, new Function method, and JSON.parse() method. For three methods, friends who need it can refer to

5. Python built-in function - repr & str

Introduction: This is consistent with the result obtained by conversion (backtick ``). As a normal function, it is sometimes useful to use this operation. For most types, this function attempts to return a string. When passed to eval(), the same object will be generated,

6. Python built-in function-compile

Introduction: This function is used to compile the source code of a string. The result can generate bytecode or AST (Abstract Syntax Tree), bytecode can be executed using the function exec(), and AST can be compiled using eval(). 2. The parameter source is the source code of a string, or an array of AST objects.

7. php How to disable eval() function instance details

## Introduction: eval is a function in PHP and cannot be disabled directly. However, the eval function is quite dangerous and often causes some problems. Today we will take a look at the operation of the eval function on arrays and how to disable the eval() function in PHP. , Friends in need can refer to

8. php eval function usage Tips on the eval() function in PHP

#Introduction: This function can substitute the variable value in the string and is usually used to process database data

9. A brief discussion on the definition and usage of PHP eval() function

Introduction: Below The editor will bring you a brief discussion on the definition and usage of the PHP eval() function. The editor thinks it’s pretty good, so I’ll share it with you now and give it as a reference. Let’s follow the editor and take a look

10. php How to disable eval() function example detailed explanation_php example

Introduction: eval is a function in php and cannot be disabled directly, but the eval function is quite dangerous and often causes some problems. Today we will take a look at the operation of the eval function on arrays and how to disable eval in php( ) function, friends who need it can refer to

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