# How to validate CVV number using Regular Expression

• Last Updated : 11 Nov, 2021

Given string str, the task is to check whether it is a valid CVV (Card Verification Value) number or not by using Regular Expression
The valid CVV (Card Verification Value) number must satisfy the following conditions:

1. It should have 3 or 4 digits.
2. It should have a digit between 0-9.
3. It should not have any alphabets and special characters.

Examples:

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Input: str = “561”
Output: true
Explanation:
The given string satisfies all the above mentioned conditions. Therefore, it is a valid CVV (Card Verification Value) number.

Input: str = “50614”
Output: false
Explanation:
The given string has five-digit. Therefore, it is not a valid CVV (Card Verification Value) number.

Input: str = “5a#1”
Output: false
Explanation: The given string has alphabets and special characters. Therefore, it is not a valid CVV (Card Verification Value) number.

Approach: The idea is to use Regular Expression to solve this problem. The following steps can be followed to compute the answer.

• Get the String.
• Create a regular expression to check valid CVV (Card Verification Value) number as mentioned below:
`regex = "^[0-9]{3, 4}\$";`
• Where:
• ^ represents the starting of the string.
• [0-9] represents the digit between 0-9.
• {3, 4} represents the string has 3 or 4 digits.
• \$ represents the ending of the string.
• Match the given string with the regular expression. In Java, this can be done by using Pattern.matcher().
• Return true if the string matches with the given regular expression, else return false.

Below is the implementation of the above approach:

## Java

 `// Java program to validate``// CVV (Card Verification Value)``// number using regex.``import` `java.util.regex.*;``class` `GFG {` `    ``// Function to validate``    ``// CVV (Card Verification Value) number.``    ``// using regular expression.``    ``public` `static` `boolean` `isValidCVVNumber(String str)``    ``{``        ``// Regex to check valid CVV number.``        ``String regex = ``"^[0-9]{3,4}\$"``;` `        ``// Compile the ReGex``        ``Pattern p = Pattern.compile(regex);` `        ``// If the string is empty``        ``// return false``        ``if` `(str == ``null``)``        ``{``            ``return` `false``;``        ``}` `        ``// Find match between given string``        ``// and regular expression``        ``// using Pattern.matcher()` `        ``Matcher m = p.matcher(str);` `        ``// Return if the string``        ``// matched the ReGex``        ``return` `m.matches();``    ``}` `    ``// Driver code``    ``public` `static` `void` `main(String args[])``    ``{` `        ``// Test Case 1:``        ``String str1 = ``"561"``;``        ``System.out.println(isValidCVVNumber(str1));` `        ``// Test Case 2:``        ``String str2 = ``"5061"``;``        ``System.out.println(isValidCVVNumber(str2));` `        ``// Test Case 3:``        ``String str3 = ``"50614"``;``        ``System.out.println(isValidCVVNumber(str3));` `        ``// Test Case 4:``        ``String str4 = ``"5a#1"``;``        ``System.out.println(isValidCVVNumber(str4));``    ``}``}`

## Python3

 `# Python3 program to validate``# CVV (Card Verification Value)``# number using regex.``import` `re` `# Function to validate``# CVV (Card Verification Value) number.``# using regular expression.`  `def` `isValidCVVNumber(``str``):` `    ``# Regex to check valid``    ``# CVV number.``    ``regex ``=` `"^[0-9]{3,4}\$"` `    ``# Compile the ReGex``    ``p ``=` `re.``compile``(regex)` `    ``# If the string is empty``    ``# return false``    ``if``(``str` `=``=` `None``):``        ``return` `False` `    ``# Return if the string``    ``# matched the ReGex``    ``if``(re.search(p, ``str``)):``        ``return` `True``    ``else``:``        ``return` `False` `# Driver code`  `# Test Case 1:``str1 ``=` `"561"``print``(isValidCVVNumber(str1))` `# Test Case 2:``str2 ``=` `"5061"``print``(isValidCVVNumber(str2))` `# Test Case 3:``str3 ``=` `"50614"``print``(isValidCVVNumber(str3))` `# Test Case 4:``str4 ``=` `"5a#1"``print``(isValidCVVNumber(str4))` `# This code is contributed by avanitrachhadiya2155`

## C++

 `// C++ program to validate the``// CVV (Card Verification Value) number``// using Regular Expression``#include ``#include ``using` `namespace` `std;` `// Function to validate the CVV``// (Card Verification Value) number``bool` `isValidCVVNumber(string str)``{` `    ``// Regex to check valid CVV``    ``// (Card Verification Value) number``    ``const` `regex pattern(``"^[0-9]{3,4}\$"``);` `    ``// If the CVV (Card Verification Value)``    ``//  number is empty return false``    ``if` `(str.empty())``    ``{``        ``return` `false``;``    ``}` `    ``// Return true if the CVV``    ``// (Card Verification Value) number``    ``// matched the ReGex``    ``if` `(regex_match(str, pattern))``    ``{``        ``return` `true``;``    ``}``    ``else``    ``{``        ``return` `false``;``    ``}``}` `// Driver Code``int` `main()``{``    ``// Test Case 1:``    ``string str1 = ``"561"``;``    ``cout << isValidCVVNumber(str1) << endl;` `    ``// Test Case 2:``    ``string str2 = ``"5061"``;``    ``cout << isValidCVVNumber(str2) << endl;` `    ``// Test Case 3:``    ``string str3 = ``"50614"``;``    ``cout << isValidCVVNumber(str3) << endl;` `    ``// Test Case 4:``    ``string str4 = ``"5a#1"``;``    ``cout << isValidCVVNumber(str4) << endl;` `    ``return` `0;``}` `// This code is contributed by yuvraj_chandra`
Output
```true
true
false
false```

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