给定前 10 个数字的范围，从开始数字迭代到结束数字并打印当前数字和前一个数字的总和

Question

I'm trying to write Python code for the above problem and getting an error code. I would appreciate help:

num = list(range(10))
previousNum = 0
for i in num:
    sum = previousNum + i
    print('Current Number '+ str(i) + 'Previous Number ' + str(previousNum) + 'is ' + str(sum)
    previousNum=i

This is the error I get:

File "<ipython-input-40-6f1cd8f8f1d7>", line 6
    previousNum=i
              ^
SyntaxError: invalid syntax

Answer 1

Looks to be a simple syntax error in line 5.

You're missing a closing parenthesis ")" at the end of your print function.

For example:

num = list(range(10))
previousNum = 0
for i in num:
    sum = previousNum + i
    print('Current Number '+ str(i) + 'Previous Number ' + str(previousNum) + 'is ' + str(sum)) # <- This is the issue.
    previousNum=i

Also, here are 3 pointers to improve your code that might be useful for you:

1. First off, Python uses snake case for it's language as described in PEP8 , so instead of typing "previousNum" you should use "previous_num", so we'll start with that.

2. Storing list(range(1)) in this instance isn't needed. You can just use the ```range(10)''' function in place of having a stored list of ranges.

3. f strings are much more readable ways of doing String Concatenation (adding strings together).

With these your code will look like this:

previous_num = 0
for i in range(10):
    sum = previous_num + i
    print(f'Current number {i} Previous Number {previous_num} is {sum}')
    previous_num = i

Happy coding!

Answer 2

sum = 0
for idx in range(10):
    print(f'current number = {idx}')
    if idx != 0:
        sum += idx
        print(f'cumul. sum = {sum}')

Answer 3

Welcome to Stackoverflow. There's always functional python:

>>> list(map( lambda x: x[0] + x[1], zip(range(0,10), range(1,11))))
[1, 3, 5, 7, 9, 11, 13, 15, 17, 19]

Or if you meant a cumulative sum of predecessors, like a reduce:

>>> [sum(range(xs)) for xs in range(1,11)]
[0, 1, 3, 6, 10, 15, 21, 28, 36, 45]

This used to be easier in python 2, before range, filter, and map were turned into iterators.

Answer 4

for i in range(1,10+1):
   print(i+i-1, end=' ')

Here it iterates from 1 to 10 inclusively. It prints the value of sum of current value of i and the previous value that is i-1