Here is the syntax for while-loops:
while <cond>: <block>
This means: repeat
<block> while the condition
<cond> is True. Stop repeating
<block> once the condition
<cond> becomes False.
Let's write the function
my_log10(n) which computes (reminder: is the number such that . For example, because .
def my_log10(n): res = 1 i = 0 #a counter for the number of times the while-loop runs while res < n: res = res * 10 i = i + 1 return i
Here is the idea: res is multiplied by 10 every time we enter the while loop, and the loop terminates when i is no longer smaller than n. The counter variable
i is incremented by 1 every iteration, so when the loop has terminated, counter contains the number iterations required to make i larger than 2 if we double i at every iteration.
Note: one execution of the block is called an "iteration."