By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. If you want to keep summing the digits until you get a single-digit number one of my favorite characteristics of numbers divisible by 9 you can do:.

Inside the for loop, the number n is converted into a string to be split with loop index i and get each digit. Learn more. Sum the digits of a number - python Ask Question. Asked 7 years, 1 month ago. Active 3 months ago. Viewed k times. If I want to find the sum of the digits of a number, i. I instinctively did: sum int digit for digit in str number and I found this online: sum map int, str number Which is best to use for speed, and are there any other methods which are even faster?

These are fine and equivalent. How are you defining best? Easiest to understand? Active Oldest Votes. Pavel Anossov Pavel Anossov Otherwise I get wrong answers. May I need an explanation here on "while n:"?

I do not know how Python understand when to stop.In this post, we will discuss how to write a python program to find the sum of digits of a number. Let's discuss these ways one by one. Here, we take the remainder of the number by dividing it by 10 then change the number to the number with removing the digit present at the unit place.

We repeat this process in the while loop. And in every iteration, we sum up the remainder till the number becomes 0.

## Python | Get first and last elements of a list

We can decrease the number of code lines by replacing the statements present in the body of while loop with just one statement. Look in the code I have put the one line statement code in the comment. In this, we will take the number as a string and then by using for loop we traverse through every digit and add it up to the sum. In this, we will define a recursive function getDigitSum. This function will return the sum of the digits.

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**Sum of digits in a number in python**

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### Python | Get first and last elements of a list

Then Subscribe to our Website.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I am brand new to programming, learning Python3 from an online course. This exercise asks me to write a program which reads a string using inputand outputs the same string but with the first and last character exchanged example: Fairy becomes yairF.

Dan hogan nashvilleThere is likely a simpler way to do this with more advanced functions, however, for the purposes of this exercise, I am supposed to write the program using only classes, substrings and indices. Here is what I have now:. Using the example of input 'Fairy', this outputs 'y air F', which is not what I'm looking for. I also tried. However, line three gave me: TypeError: 'str' object does not support item assignment.

So I'm guessing I can't assign new values to places in an index. My other approach, below, also gave me an error:. Line three gave me: TypeError: decoding str is not supportedso it seems that I can't combine them that way. Any tips on handling this? To swap letters in a string, you can make it into a list then simply change the order of the list:. I stumbled upon to this question too, and after reading the answers I found probably the easiest way to do it:. Learn more. Asked 6 years, 10 months ago.

Active 18 days ago. Viewed 19k times. Active Oldest Votes. You can do magic with it. Please don't name a variable strit's the name of the type. Kay: Works for strings of any length as written. Benjamin Toueg Benjamin Toueg 8, 6 6 gold badges 36 36 silver badges 67 67 bronze badges.

How to disable google keyboard xiaomiTerryA TerryA However doesn't handle empty strings.Sometimes, there might be a need to get the range between which a number lies in the list, for such applications we require to get the first and last element of the list. Method 1 : Using list index Using the list indices inside the master list can perform this particular task.

This is most naive method to achieve this particular task one can think of. Method 2 : Using List slicing One can also make use of list slicing technique to perform the particular task of getting first and last element.

We can use step of whole list to skip to the last element after the first element. Method 3 : Using list comprehension List comprehension can be employed to provide a shorthand to the loop technique to find first and last element of the list.

Plumbers apprenticeNaive method of finding is converted to a single line using this method. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.

See your article appearing on the GeeksforGeeks main page and help other Geeks. Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below. Writing code in comment? Please use ide. Python3 code to demonstrate. Output: The original list is : [1, 5, 6, 7, 4] The first and last element of list are : [1, 4].

Check out this Author's contributed articles. Load Comments.Sometimes, there might be a need to get the range between which a number lies in the list, for such applications we require to get the first and last element of the list. Method 1 : Using list index Using the list indices inside the master list can perform this particular task.

This is most naive method to achieve this particular task one can think of. Method 2 : Using List slicing One can also make use of list slicing technique to perform the particular task of getting first and last element.

We can use step of whole list to skip to the last element after the first element. Method 3 : Using list comprehension List comprehension can be employed to provide a shorthand to the loop technique to find first and last element of the list. Naive method of finding is converted to a single line using this method. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.

See your article appearing on the GeeksforGeeks main page and help other Geeks. Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Writing code in comment? Please use ide. Python3 code to demonstrate.

Work manager android exampleOutput: The original list is : [1, 5, 6, 7, 4] The first and last element of list are : [1, 4]. Recommended Posts: Python Merge List with common elements in a List of Lists Python Sorting list of lists with similar list elements Python Add list elements with a multi-list based on index Python Subtract two list elements if element in first list is greater Python Replace elements in second list with index of same element in first list Python Maximum sum of elements of list in a list of lists Python Indices of sorted list of list elements Python - Replace index elements with elements in Other List Python Get last N elements from given list Python Index of Non-Zero elements in Python list Python Absolute value of list elements Python - Get Indices of Even Elements from list Python List frequency of elements Python Merge list elements Python Remove last K elements of list.

Check out this Author's contributed articles. Load Comments.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Is there a command to check the first two digits of a number?

Both of the previous 2 answers have at least O n time complexity and the string conversion has O n space complexity too. Here's a solution for constant time and space:. You will need to add some checks if it's possible that your input number has less digits than you want. Comparing the O n time solution with the "constant time" O 1 solution provided in other answers goes to show that if the O n algorithm is fast enough, n may have to get very large before it is slower than a slow O 1.

The strings version is approx. They become closer only when then number of digits approaches digits. The regular expression 1[56] matches a 1 followed by either a 5 or a 6 and stores the result in the first capturing group.

Learn more. How can I get the first two digits of a number? Ask Question. Asked 3 years, 3 months ago. Active 8 months ago. Viewed 69k times. I want to check the first two digits of a number in Python. ThisSuitIsBlackNot John28 John28 1 1 gold badge 5 5 silver badges 11 11 bronze badges. Convert to string and check if first two symbols are "15". Sorry Dinesh Pundkar. Yes I mean the first two digit of number Active Oldest Votes. I originally came here for a math-based answer, but found this string-based solution is faster than the other math-based answer provided.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

### Find first and last digits of a number

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information.

I want to write a program for finding out the sum of first and the last digit of any number entered through keyboard. For example, I entered As for the first digit, I'm not sure about the most efficient way to get that. The first thought that immediately springs to my mind is:. A much more efficient way to go about doing this would be to find the number of digits beforehand, like so:.

This should work. Since the input is an array you just need to to look at the zero element and the last one, then sum them up. Learn more. Finding out the sum of first and the last digit of any number Ask Question.

Asked 9 years, 7 months ago. Active 3 years, 7 months ago. Viewed 20k times. Yes, this is an assignment. Foo Bah Must be homework. How else could this possibly be practical? Ah well, then There is no benefit in converting the whole input string to an integer, on the opposite.

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