I am relatively new to programming and am having trouble with a simple while loop. I am attempting to write a program that outputs all multiples of 3 between 0 and 100. Here is what I have:
counter3 = 1
theList = []
while counter3 <= 1000:
if 3 % counter3 : True
theList.append(counter3)
counter3 = counter3+1
print(theList)
The while loop I am using has a syntax error, but I am not sure where it is. Any help would be appreciated
When the code you used is ran, it does not throw a syntax error. It instead returns a list of the numbers from 1 to 1000. The reason why is the following statement:
if 3 % counter3 : True
theList.append(counter3)
The : operator denotes the end of the if statement, and what is placed after that is executed if the statement is true. In this scenario, you would want to replace the : with a ==. Since the if statement is executed automatically if 3 % counter3 is true, then you don't need == true at all.
Then, you would want to indent theList.append(counter3), so that it runs if the statement is true. New code:
counter3 = 1
theList = []
while counter3 <= 1000:
if 3 % counter3:
theList.append(counter3)
counter3 = counter3+1
print(theList)
However, it still prints the numbers from 1 to 1000. This is because the numbers used in the % operator are on the wrong sides. You want to check if the number is divisible by 3, using the line if counter3 % 3:.
Now it prints everything except numbers divisible by 3. This is because a number divisible by 3 will return 0. 0 is a falsy value, which means it evaluates to false in the if statement. 1 and 2 (the other options) evaluate to true.
Falsy values are False, 0, [], "", 0.0, 0j, (), {}, and set().
Check this link for details.
Since you want to check if it is divisible by 3, then you want to check if the number mod 3 is equal to 0. Now your code is the following:
counter3 = 1
theList = []
while counter3 <= 1000:
if counter3 % 3 == 0:
theList.append(counter3)
counter3 = counter3+1
print(theList)
You could do if not counter3 % 3, as 0 is falsy, but that obscures the function of your code and is not a good practice.
Since your question says to do numbers between 0 and 100, you should change the while statement to while counter3 <= 100:.
Another thing is that you should probably use a for loop. This lets you iterate over a range, allowing you to not have to keep track of the variable and increment it over time.
theList = []
for counter3 in range(1, 100):
if counter3 % 3 == 0:
theList.append(counter3)
print(theList)
This code works, and it observes most best practices.
If you wanted to, you could use a list comprehension for a one-liner, but this wouldn't be needed.
print([i for i in range(1, 100) if i % 3 == 0])
print([i * 3 for i in range(1, 34)]) #Prints first 33 numbers multiplied by 3, has the same result.
To tell if a number is a multiple of three, it should be
if counter3 % 3 == 0:
counter3 % 3 computes the remainder of counter3 / 3, and this remainder is 0 for exact multiples.
Then you need to indent the statements that should be executed when this condition is true.
So the loop should be:
while counter3 <= 1000:
if counter3 % 3 == 0:
theList.append(counter3)
counter3 = counter3+1
Instead of a while loop, you can use for:
for counter3 in range(1, 1001):
if counter3 % 3 == 0:
theList.append(counter3)
