Question

I am writing some code to gain practice programming Python. The code is as follows:

#! /usr/bin/python

string ='''
73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450'''.replace('\n','')

sum1 = 1
lis = [0,1,2,3,4]
lis2 = list()
while(1):
    for j in range(5):
        sum1 *= int(string[ lis[j] ])
    lis2.append(sum1)
    sum1 = 1
    for k in range(5):
        lis[k] = lis[k] + 1
    if lis[4] == 999:
        break
lis2.sort() 
print lis2

The program is used to find the greatest product of five consecutive digits in the 1000-digit number.

But the program didn’t work! An error

ValueError: invalid literal for int() with base 10:

occured when I ran the program!

I am a newbie to python!

Answer 1

Your problem is simple: Python triple-quote strings include the line ending. There is a “newline” character at the end of each line, and int() is not happy.

Easiest solution is to use the string .replace() method to remove the non-wanted newline characters. We use "\n" for a newline:

string = """
012345
242432
234323""".replace('\n', '')

After I make that change, your program still doesn’t work, but that particular problem is gone.

EDIT:
To improve your program, I suggest you read up on “slicing” of strings in Python. You can use slicing to grab 5 characters at a time from the input string. Also, Python can loop over a string with an ordinary for loop, so you can get a 5-character slice and loop over it to multiply the five digits together.