0

# Sigma Notation for Exponential Summations

Working on another piece of code that requires the use of sigma notation. Specifically, how would one represent the following sigma summation in python?: Σ (10^k), k=0 to n

26th Dec 2019, 2:27 AM
Pythagoras + 4
Just run a loop for k from 0 to n, and for each iteration add (10^k) to some variable sum which was initialized as 0 before loop. After loop ends, sum will give value of above summation. Here it will be, 1+10+100+...+100000(n zeroes) = 111...1(n+1 ones)
26th Dec 2019, 2:50 AM
Gaurav Agrawal + 3
Pythagoras you are giving wrong value to y in first statement of each iteration, if you are using y in purpose to get summation.
26th Dec 2019, 2:53 AM
Gaurav Agrawal 0
I tried: for i in range(some_num): y = 10**k y += y But it did not return the correct values.
26th Dec 2019, 2:52 AM
Pythagoras 0
Ok, thank you for your help.
26th Dec 2019, 3:09 AM
Pythagoras 0
You could also use the built-in sum function which takes as argument an iterable of numbers: sum((1.3, 5.5)) # 6.8 sum(range(100+1)) # 5050 sum(10**k for k in range(6)) # 111111 type(10**k for k in range(6)) # <class 'generator'> or for your special case: int("1" * 6) # 111111 For strings you could use ''.join(iterable_of_strings): ''.join(map(str.title, ['ba, 'na', 'na'])) # BaNaNa and for lists you could make your own (works on any type which has + defined for them which also includes ints and strings): from functools import reduce reduce(lambda x, y: x + y, ([1, 2], [3, 4, 5], [])) # [1, 2, 3, 4, 5]
26th Dec 2019, 6:22 AM
Zuke 