- Definite iteration has a set of instructions that are repeated a specific number of times that is specified in advance. It is implemented by using count-controlled loops, such as for loops

- Indefinite iteration has a set of instructions that is repeated until a condition is met. It is implemented by using condition-controlled loops, such as while loops.

Definite vs Indefinite Iteration

While loops can allow a programmer to execute the same block of code repeatedly while a condition evaluates to true. The condition may be a result of a comparison, or the value of a variable. Non-zero variables and non-empty collections will evaluate to true, while the opposite will evaluate to false.

```python
x = 5
while x > 0:
   print(f"{x} seconds to launch")
   x = x - 1
print("Take Off!")
```
Result:
```
5 seconds to launch
4 seconds to launch
3 seconds to launch
2 seconds to launch
1 second to launch
Take Off!
```

University of Michigan - Ann Arbor

A statement is any line of instruction that the Python interpreter can potentially execute. 

Types of statements include but are not limited to:
- Variable assignment statements 
- while statements
- for statements
- if statements
- import statements 

Statements in Python 

W3Schools offers online tutorials about different parts of programming in Python: https://www.w3schools.com/python/default.asp

W3Schools Python Tutorial

These are all examples of different kinds of Python Statements:
- x = 3.14159
- mean_price = 12.35/4
- import turtle
- for _ in range(7):
    billy.forward(5)
- print("This line will execute once")

Examples of Statements in Python 

The use of a for loop can allow for the programmer to make repetitive outputs or actions. The for loop will search through an iterable in order to do something with each element in it.

```python
for _ in range(5):
    print("This will print 5 times.")
```
Result:
```
This will print 5 times.
This will print 5 times.
This will print 5 times. 
This will print 5 times. 
This will print 5 times. 
```


For Loops

Modules are files which can be thought of as packages containing functions and definitions meant for use in Python programming. Importing can be done through the use of import statements.
```
import turtle
import random
import aifc 
```
^The above statements import the turtle module, random module, and aifc module, respectively.

Importing Modules 


- If statement evaluates a boolean expression and  then executes a set of statements based on the output of the boolean expression.
 
- if ,elif and else are keywords that help to achieve conditional execution of statements.


Syntax


if boolean expression:

         statements

elif boolean expression:

        statements

else:

        statements



If Statements

While Loops

With the break statement we can stop or break out of the loop before it has looped through all the items:
```python
tasks = ["Eat", "Sleep", "Repeat"]
for x in tasks:
  print(x)
  if x == "Sleep":
    break
```
In the example above, the code will print ```Eat```  ```Sleep``` then the loop will ```break``` and ```Repeat``` will not be printed.


Break Statement

Comments are used to explain python code and make the code easier to read. They aren't considered actual code and are essentially ignored during compilation. We can write a single line comment using # symbol
```python
#this function takes two integers and prints the sum
def sum(x,y):
    print(x+y)
```
The comment explains the purpose of the function ```sum```

For a multiline comment, we can just put the comment inside triple quotes.
```python
"""
these lines
are
ignored
"""
print("Hello World")
```

Python Comments

The continue statement is used to ignore specific iterations of a loop and go onto the next iteration instead. Once the statement is reached and its conditions are met, control jumps back to the top of the loop, ignoring any remaining code in the loop body. In this example, the number 3 won't be printed.

```python
x = 0
while x < 5:
    x = x + 1
    if x == 3:
        continue
    print(f"{x}")
```
Continue statements work similarly to break statements, but they only end a single iteration of the loop, not the entire loop itself.

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