Adjacent number multiplication in a string.

Question

Hello, sololearners.

Let's assume I have a list with 6 digit numbers as a string. The length of list is N (unknown).

So we have:

ls = ['123456', '789123', '456789', and so on... ]

How can I loop through each of the string, and multiply each number?

e.g. 123456 = 1x2x3x4x5x6 = 720
e.g. 789123 = 7x8x9x1x2x3 = 3024

I tried nested for loop, such that:

n = 0
for x in ls:
for l in x:
n += int(l)*int(l)

and tried to compare products of values followed by if statements, but it didn't work.

Any suggestions how can I loop through each of the string, and multiply each number?

Answer 1

Lamron ,

first step is to get the string of numbers to individual digits:

> use a for loop to iterate over the list. take the string of digits and convert it to a list. this will separate the digits, but they are still strings.
> in the same step we can use map() function and make each of the *string digits* an integer value.
...
temp_lst = list(map(int, list(<string_of_digits>)))

second step is to multiply the digits:

> to get the product, we can use an additional loop and build the result of all digits.
or
> we can use the prod() method from the math module, that takes a list of int numbers and returns the result.

Answer 2

Lamron ,

your assumption is correct.

if we have a list with 5 strings of digits, and we iterate over them, we will get each of the strings from the list.

> in each loop iteration we get 1 string e.g. => '123456', that we can convert to a list => ['1', '2', '3', '4', '5', '6']

> applying map(int, ...) converts the list as => [1, 2, 3, 4, 5, 6].

> now as we have a list of integers, we can calculatd the product.

*this is the basic version using 2 nested for loops*

nums_lst = ['123456', '789123', '456789', '123']
for num in nums_lst:
total = 1
for dig in num:
total *= int(dig)
print(total)

Answer 3

Mirielle ,

*readability counts*

Answer 4

Thanks for explanation and guidance, Lothar

Thanks for your cheat Mirielle

Answer 5

You can also use the ord() function to get the digit character's ASCII code. With a bit of value manipulation we can have a for...loop do something that we want.

Here's how it goes ...

lst = [ "123456", "789123", "3278433" ]

def digit_prod( s ):
if not s.isdigit():
return 0 # for non-numeric strings
rv = 1
for c in s:
rv *= ord( c ) - 48
return rv

result = list( map( digit_prod, lst ) )
print( result ) # 720 3024 12096

(Edited)

Answer 6

Ipang I'll try that code too and see how it goes!

Answer 7

Lothar , what do you mean by this:

"
> use a for loop to iterate over the list. take the string of digits and convert it to a list. list will separate the digits, but they are still strings.
"

Does it mean, if I have in total 5 items in **ls** , I will have to make a separate list for each of these items to split digits? Or is it implemented somehow different?

Answer 8

And others might say lambda is scary.
As long as it works, it's all good

Answer 9

These all seem to be interesting

Answer 10

Oparah anord welcome to sololesrn.

Don't hesitate to read this post, and make your way through courses that suit you the best:

https://www.sololearn.com/Discuss/3021159/?ref=app