# Python: Return from cycles

Working with loops usually comes down to two scenarios:

- Aggregation. Accumulation of result during iterations and working with it after the cycle. Line reversal refers to this variant.
- Executing the loop until the desired result is achieved and exiting. For example, the problem of searching for prime numbers - which are divided without remainder by themselves and by one

Consider the algorithm for checking the simplicity of a number. We will divide the sought number `x`

by all numbers in the range from two to `x - 1`

and see the remainder. If no divisor is found in this range, which divides the number `x`

without a remainder, then we have a prime number.

In this case it is enough to check the numbers not up to `x - 1`

, but up to half a number. For example, 11 is not divisible by 2, 3, 4, 5. But further will not divide by numbers greater than its half. So, we can optimize the algorithm and check the division only up to `x / 2`

:

```
def is_prime(number):
if number < 2:
return False
divider = 2
while divider <= number / 2:
if number % divider == 0:
return False
divider += 1
return True
print(is_prime(1)) # => False
print(is_prime(2)) # => True
print(is_prime(3)) # => True
print(is_prime(4)) # => False
```

Imagine that the algorithm of consecutive division by numbers up to `x / 2`

has found one that divides without a remainder. So the argument passed is not a prime number, and further calculations do not make sense. At this point it returns `False`

.

If the whole cycle worked and no number was found that divides without a remainder, it means that the number is prime.

## Instructions

Implement a function `is_contains_char()`

that checks case-sensitively if a string contains a specified letter. The function takes two parameters:

- The line
- Search letter

```
print(is_contains_char('Hexlet', 'H')) # => True
print(is_contains_char('Hexlet', 'h')) # => False
print(is_contains_char('Awesomeness', 'm')) # => True
print(is_contains_char('Awesomeness', 'd')) # => False
```

## The exercise doesn't pass checking. What to do? 😶

If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:

- Be sure to attach the test output, without it it's almost impossible to figure out what went wrong, even if you show your code. It's complicated for developers to execute code in their heads, but having a mistake before their eyes most probably will be helpful.

## In my environment the code works, but not here 🤨

Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.

## My code is different from the teacher's one 🤔

It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.

In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.

## I've read the lessons but nothing is clear 🙄

It's hard to make educational materials that will suit everyone. We do our best but there is always something to improve. If you see a material that is not clear to you, describe the problem in “Discussions”. It will be great if you'll write unclear points in the question form. Usually, we need a few days for corrections.

By the way, you can participate in courses improvement. There is a link below to the lessons course code which you can edit right in your browser.