there is a lot of information about how to write Luhn algortim. I'm trying it too and I think that I'am very close to succes but I have some mistake in my code and dont know where. The test card is VALID card but my algorithm says otherwise. Don't you know why? Thx for help
test = "5573497266530355"
kazde_druhe = []
ostatni = []
for i in test:
if int(i) % 2 == 0:
double_digit = int(i) * 2
if double_digit > 9:
p = double_digit - 9
kazde_druhe.append(p)
else:
kazde_druhe.append(double_digit)
else:
ostatni.append(int(i))
o = sum(ostatni)
k = sum(kazde_druhe)
total = o+k
if total % 10 == 0:
print(f"Your card is valid ")
else:
print(f"Your card is invalid ")
Finally! Thank you all for your help. Now it is working :-)
test = "5573497266530355" kazde_druhe = [] ostatni = []
for index, digit in enumerate(test):
if index % 2 == 0:
double_digit = int(digit) * 2
print(double_digit)
if double_digit > 9:
double_digit = double_digit - 9
kazde_druhe.append(double_digit)
else:
kazde_druhe.append(double_digit)
else:
ostatni.append(int(digit))
o = sum(ostatni)
k = sum(kazde_druhe)
total = o+k if total % 10 == 0:
print(f"Your card is valid ")
else:
print(f"Your card is invalid ")
From this description
2. With the payload, start from the rightmost digit. Moving left, double the value of every second digit (including the rightmost digit).
You have to check the digit position, not the number itself.
Change to this:
for i in range(len(test)):
if i % 2 == 0:
This code works. :)
I fixed you code as much as i could.
test = "5573497266530355"
#test = "3379513561108795"
nums = []
for i in range(len(test)):
if (i % 2) == 0:
num = int(test[i]) * 2
if num > 9:
num -= 9
nums.append(num)
else:
nums.append(int(test[i]))
print(nums)
print((sum(nums) % 10) == 0)
I found where your code went wrong.
On the line:
for i in test:
if int(i) % 2 == 0:
It should be:
for i in range(len(test)):
if i % 2 == 0:
You should not be using the element of the string you should be using the index of the element.
Related
I'm trying to create a program that checks whether the credit card number the user inputed is either invalid, or from AMEX, MASTERCARD, or VISA. I'm using Luhn's formula. Here is a site that contains the explanation to the formula I'm using: https://www.geeksforgeeks.org/luhn-algorithm/
It works with all credit card numbers, except credit cards from AMEX. Could someone help me?
Here is my code:
number = input("Number: ")
valid = False
sumOfOdd = 0
sumOfEven = 0
def validation(credit_num):
global sumOfOdd
global sumOfEven
position = 0
for i in credit_num:
if position % 2 != 0:
sumOfOdd += int(i)
else:
product_greater = str(int(i) * 2)
if len(product_greater) > 1:
sumOfEven += (int(product_greater[0]) + int(product_greater[1]))
else:
sumOfEven += int(product_greater)
position += 1
def main():
if (sumOfOdd + sumOfEven) % 10 == 0:
if number[0] == "3":
print("AMEX")
elif number[0] == "5":
print("MASTERCARD")
else:
print("VISA")
else:
print("INVALID")
print(f"{sumOfOdd + sumOfEven}")
validation(number)
main()
Here are some credit card numbers:
VISA: 4111111111111111
MASTERCARD: 5555555555554444
AMEX: 371449635398431
I've found many different ways to calculate this formula, but I'm not sure if mine is correct.
I am asked to binary search a list of names and if these names start with a particular letter, for example A, then I am to print that name.
I can complete this task by doing much more simple code such as
for i in list:
if i[0] == "A":
print(i)
but instead I am asked to use a binary search and I'm struggling to understand the process behind it. We are given base code which can output the position a given string. My problem is not knowing what to edit so that I can achieve the desired outcome
name_list = ["Adolphus of Helborne", "Aldric Foxe", "Amanita Maleficant", "Aphra the Vicious", "Arachne the Gruesome", "Astarte Hellebore", "Brutus the Gruesome", "Cain of Avernus"]
def bin_search(list, item):
low_b = 0
up_b = len(list) - 1
found = False
while low_b <= up_b and found == False:
midPos = ((low_b + up_b) // 2)
if list[midPos] < item:
low_b = midPos + 1
elif list[midPos] > item:
up_b = midPos - 1
else:
found = True
if found:
print("The name is at positon " + str(midPos))
return midPos
else:
print("The name was not in the list.")
Desired outcome
bin_search(name_list,"A")
Prints all the names starting with A (Adolphus of HelBorne, Aldric Foxe .... etc)
EDIT:
I was just doing some guess and check and found out how to do it. This is the solution code
def bin_search(list, item):
low_b = 0
up_b = len(list) - 1
true_list = []
count = 100
while low_b <= up_b and count > 0:
midPos = ((low_b + up_b) // 2)
if list[midPos][0] == item:
true_list.append(list[midPos])
list.remove(list[midPos])
count -= 1
elif list[midPos] < item:
low_b = midPos + 1
count -= 1
else:
up_b = midPos - 1
count -= 1
print(true_list)
Not too sure if this is what you want as it seems inefficient... as you mention it seems a lot more intuitive to just iterate over the entire list but using binary search i found here i have:
def binary_search(seq, t):
min = 0
max = len(seq) - 1
while True:
if max < min:
return -1
m = (min + max) // 2
if seq[m][0] < t:
min = m + 1
elif seq[m][0] > t:
max = m - 1
else:
return m
index=0
while True:
index=binary_search(name_list,"A")
if index!=-1:
print(name_list[index])
else:
break
del name_list[index]
Output i get:
Aphra the Vicious
Arachne the Gruesome
Amanita Maleficant
Astarte Hellebore
Aldric Foxe
Adolphus of Helborne
You just need to found one item starting with the letter, then you need to identify the range. This approach should be fast and memory efficient.
def binary_search(list,item):
low_b = 0
up_b = len(list) - 1
found = False
midPos = ((low_b + up_b) // 2)
if list[low_b][0]==item:
midPos=low_b
found=True
elif list[up_b][0]==item:
midPos = up_b
found=True
while True:
if found:
break;
if list[low_b][0]>item:
break
if list[up_b][0]<item:
break
if up_b<low_b:
break;
midPos = ((low_b + up_b) // 2)
if list[midPos][0] < item:
low_b = midPos + 1
elif list[midPos] > item:
up_b = midPos - 1
else:
found = True
break
if found:
while True:
if midPos>0:
if list[midPos][0]==item:
midPos=midPos-1
continue
break;
while True:
if midPos<len(list):
if list[midPos][0]==item:
print list[midPos]
midPos=midPos+1
continue
break
else:
print("The name was not in the list.")
the output is
>>> binary_search(name_list,"A")
Adolphus of Helborne
Aldric Foxe
Amanita Maleficant
Aphra the Vicious
Arachne the Gruesome
Astarte Hellebore
Objective: Write a function that takes an integer as its only parameter and returns the ordinal abbreviation for that integer as its only result. For example, if your function is passed the integer 1 then it should return the string "1st". If it is passed the integer 12 then it should return the string "12th". If it is passed 2003 then it should return the string "2003rd". Your function must not print anything on the screen.
def convert (n):
self.num = num
n = int(self.num)
if 4 <= n <= 20:
suffix = 'th'
elif n == 1 or (n % 10) == 1:
suffix = 'st'
elif n == 2 or (n % 10) == 2:
suffix = 'nd'
elif n == 3 or (n % 10) == 3:
suffix = 'rd'
elif n < 100:
suffix = 'th'
ord_num = str(n) + suffix
return ord_num
def main ():
day = int(input("Enter the day:"))
month = int(input("Enter the month:"))
year = int(input("Enter the year:"))
print("on the %n" %n, convert(day), "day of the %n" %month,
convert(month), "month of the %n" %year, convert(year),",
something amazing happened!")
main()
This is my code however it keeps saying I haven't defined n when I run it. But above I've already defined it so not sure what the problem is.
This is probably closer to what you want:
def convert(n):
n = int(n)
suffix = ''
if 4 <= n <= 20:
suffix = 'th'
elif n == 1 or (n % 10) == 1:
suffix = 'st'
elif n == 2 or (n % 10) == 2:
suffix = 'nd'
elif n == 3 or (n % 10) == 3:
suffix = 'rd'
elif n < 100:
suffix = 'th'
return str(n) + suffix
def main ():
day = int(input("Enter the day: "))
month = int(input("Enter the month: "))
year = int(input("Enter the year: "))
print("on the %s day of the %s month of the %s, something amazing happened!" %
(convert(day), convert(month), convert(year)))
main()
There are few issues. You cannot use n in main() when you define it in convert(). Also %n is not a valid format character. You need to define suffix = '' when also want run the year through the conversion function as the year can be larger than 100. Also, you probably copied the code from within a class definition. I removed the self.
Hello I'm asking about the conversion issue with strings and integers.
I have a piece code that requires the conversion between strings and integers but I just can't get it to work, I wonder if anyone could help me. I receive String index out of range error.
Here is the code
def ISBN(bc):
total = 0
up = 0
down = 11
for x in range(10):
sbc = str(bc)
ibc = int(sbc[up])
total += (ibc * down)
#total += (int(sbc[up])*down)
up += 1
down -+ 1
mod = (total % 12)
if mod == 10:
total = "x"
print ("The ISBN book code is: " + bc + total)
w = 0
while w == 0:
a = int(input("Please input the 10 digit book number:\n"))
b = str(a)
if len(b) == 9:
ISBN(a)
else:
print ("Sorry book code not 10 digits long")
restart = input("Would you like to use the book code changer again?\n")
restart = restart.lower
if restart == "yes" or restart == "y":
print ("--------------------------------------------------\n")
elif restart == "no" or restart == "n":
print ("Thank you for using the ISBN book code changer\n")
w = 1
if len(b) == 9:
This should be 10.
mod = (total % 12)
This should be 11.
So, I'm quite nooby at python. I decided to make a program that makes prime numbers. I know there's probably a function built in that does this but I decided to do it myself.
number = 1
numlist = list()
for x in range (0, 1000):
numlist.append("")
print "Created list entry " + str(x)
while True:
number = number + 1
if number % 2 != 0:
numscrollerA = 1
numscrollerB = 1
while numscrollerA <= number:
if float(number) / float(numscrollerA) == float(int(number)):
numlist[numscrollerA] = "true"
if float(number) / float(numscrollerA) != float(int(number)):
numlist[numscrollerA] = "false"
numscrollerA = numscrollerA + 1
while numscrollerB <= number:
if numscrollerB != 1 and numscroller != number and numlist[numscrollerB] == "true":
primestatus = "false"
else:
primestatus = "true"
if primestatus == "true":
print number
I get "Created list entry x" 1000 times as I should. Then the program just hangs.
while numscrollerB <= number:
if numscrollerB != 1 and numscroller != number and numlist[numscrollerB] == "true":
primestatus = "false"
else:
primestatus = "true"
You don't increase numscrollerB in this loop, so it runs infinitedly. Anyway, You should rather use 'for loop':
for numscrollerB in range(1, number+1):
pass # do something
Your code is very unpythonic. Typical of a newcomer experienced in a different style of coding.
Your list is uneccessary.
In python you could create the list like this
def check_even(val):
#this contains your logic
return val % 2 == 0
evenslist = [check_even(i) for i in xrange(1, 1001)]
print numlist