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The task is to write function that foldes number into prime factors. By given number 'n' this function should return a list of tuples p_i,c^i, for example if input is 100, the output is (2,2),(5,2).
So, here is how i try to write it:

def factor(n):
c = 1
pre_ans = list()
temp_n=n
for i in range(2,temp_n+1):
 if (is_prime(i) == True) and (temp_n % i == 0):
 for j in range (2,temp_n+1):
 if (temp_n % (i ** j) == 0):
 pre_ans.append((i,j))
 temp_n /= (i **j)
 pre_ans.append((i,c))
 temp_n /= i
print(pre_ans)

It works wrong but I can't find a mistake :(

Your general idea is ok. However there are some minor issues with the following part of your code:

for j in range (2,temp_n+1):
 if (temp_n % (i ** j) == 0):
 pre_ans.append((i,j))
 temp_n /= (i **j)
pre_ans.append((i,c))
temp_n /= i

In fact the main problem is that you need to iterate in the other direction in this statement for j in range (2,temp_n+1). If you rewrite it like

def factor(n):
 c = 1
 pre_ans = list()
 temp_n=n
 for i in range(2,temp_n+1):
 if (is_prime(i) == True) and (temp_n % i == 0):
 for j in range (temp_n+1, 0,-1):
 if (temp_n % (i ** j) == 0):
 pre_ans.append((i,j))
 temp_n /= (i **j)
 print(pre_ans)

it will work. The whole code can also get written a bit shorter:

from collections import Counter

def factor(n):
 lst = 
 for i in range(2, n+1):
 while n % i == 0:
 lst.append(i)
 n = n / i
 return Counter(lst).items()

print(factor(100))

Fixed the code. This is working version

def factor(n):
c = 1
pre_ans = list()
temp_n=n
for i in range(2, n // 2 + 1):
 if (is_prime(i) == True):
 k = 1
 while temp_n % (i ** k) == 0:
 if temp_n % (i ** (k + 1)) == 0:
 k += 1
 else:
 k += 1
 break
 if k > 1:
 pre_ans.append((i, k - 1))
return pre_ans