ATM machines allow 4 or 6 digit PIN codes and PIN codes cannot contain anything but exactly 4 digits or exactly 6 digits. If the function is passed a valid PIN string, return true, else return false

Sure, here's a Python function that checks if a PIN string is valid according to the given conditions:

def validate_pin(pin):
    if len(pin) == 4 or len(pin) == 6:
        if pin.isdigit():
            return True
    return False

You can use this function by passing a PIN string to it. It will return `True` if the PIN is valid (contains exactly 4 or 6 digits only), and `False` otherwise.

相关问题

Notice that the number 123456789 is a 9-digit number consisting exactly the numbers from 1 to 9, with no duplication. Double it we will obtain 246913578, which happens to be another 9-digit number consisting exactly the numbers from 1 to 9, only in a different permutation. Check to see the result if we double it again! Now you are suppose to check if there are more numbers with this property. That is, double a given number with k digits, you are to tell if the resulting number consists of only a permutation of the digits in the original number. Input Specification: Each input contains one test case. Each case contains one positive integer with no more than 19 digits. Output Specification: For each test case, first print in a line "Yes" if doubling the input number gives a number that consists of only a permutation of the digits in the original number, or "No" if not. Then in the next line, print the doubled number. Sample Input: 1234567899 Sample Output: Yes 2469135798

首先，我们需要将输入的数转换成字符串，并计算出它的长度。接着，我们将该数乘以2，再将结果转换成字符串，并且将它的长度与原始字符串的长度进行比较。如果长度不同，那么乘以2得到的数字肯定不是原始数字的排列。如果长度相同，那么我们需要逐一检查乘以2得到的数字中的每一个数字，确保它们在原始数字中都存在且出现的次数相同。如果满足这个条件，那么乘以2得到的数字就是原始数字的排列，否则就不是。

下面是实现这个算法的代码：

(Replace words) Suppose you have a lot of files in a directory that contain words Exercisei_j, where i and j are digits. Write a program that pads a 0 before i if i is a single digit and 0 before j if j is a single digit. For example, the word Exercise2_1 in a file will be replaced by Exercise02_01. In Java, when you pass the symbol * from the command line, it refers to all files in the directory (see Supplement III.V). Use the following command to run your program: java Exercise12_27 *

Certainly, I can help you with that! Here's a Python code snippet that can accomplish the task:

import os

for filename in os.listdir('.'):
    if filename.startswith('Exercise'):
        new_filename = filename.replace('_', '_0')
        new_filename = new_filename[:9] + '0' + new_filename[9:11] + '0' + new_filename[11:]
        os.rename(filename, new_filename)

This code loops through all files in the current directory, and checks if the filename starts with "Exercise". If it does, it replaces the first underscore with "_0". It then inserts a "0" before the first digit (if necessary) and another "0" before the second digit (if necessary). Finally, it renames the file to the new name using the `os.rename()` function. You can run this script by saving it as a .py file and executing it with the command `python filename.py` in the directory with the files.