Course Content

Learn Python from Scratch

1. The basics

Hello, World!Hello, me!Variables Comments Indentation Numbers and strings

2. Arithmetic operations

Addition Multiplication and power Division and whole part division

3. Common data types

Data types Numbers float and int Storing text Strings slicing Concatenation

4. Conditional statements

Boolean data type Combining conditions Simple if/else expressions (1/2)Simple if/else expressions (2/2)If/else expressions with multiple conditions (1/2)If/else expressions with multiple conditions (2/2)

5. Other data types

Lists (1/3)Lists (2/3)Lists (3/3)Tuples (1/3)Tuples (2/3)Tuples (3/3)Dictionaries (1/2)Dictionaries (2/2)

6. Loops

while loop (1/2)while loop (2/2)for loop (1/5)for loop (2/5)for loop (3/5)for loop (4/5)for loop (5/5)

7. Functions

Built-in functions Writing your own functions (1/5)Writing your own functions (2/5)Writing your own functions (3/5)Writing your own functions (4/5)Writing your own functions (5/5)lambda functions

while loop (2/2)

As we mentioned before, sometimes we don't exactly know the stopping condition. In that case, we first need to start an infinite loop and then specify the stopping condition. If you want to start an infinite loop, use while True.

There are two important commands in Python: break and continue. break will break the loop and go outside loop to the next line. continue will skip all the rest code inside loop and return at its beginning.

For example, imagine we have number 3 and want to reach number 6. All we can do - is to add 2 and subtract 1.


              12345678910111213141516
            
# starting number
a = 3

# let's construct while loop
while True: # infinite loop
  if a == 6: # stopping condition
    print("Number", a, "reached")
    break # this will break loop
  elif a < 6: # if less, than add 2
    a = a + 2
    print("Adding 2... Reached", a)
    continue # returning to loop start
  else: # if greater, then subtract 1
    a = a - 1
    print("Subtracting 1... Reached", a)
    continue # returning to loop start

If we didn't specify break in the first if, then we got an infinite loop, because 6 is not satisfying any other condition but the first one. In that case, it printed us "Number 6 reached" infinite times.

Task

Using while loop and continue/break commands construct the next program:

Given number a = -7. At each step if the number is negative, you need to print "a is negative, and =" and value, and then add 4 and continue the loop. If the number is positive, you need to print "a is positive, and =" and its value after = sign. In that case you need to subtract 3 and continue the loop. If the number is zero - you need to print "Finally a is zero!" and break the loop.

Task

Using while loop and continue/break commands construct the next program:

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Section 6. Chapter 2

while loop (2/2)

For example, imagine we have number 3 and want to reach number 6. All we can do - is to add 2 and subtract 1.


              12345678910111213141516
            
# starting number
a = 3

# let's construct while loop
while True: # infinite loop
  if a == 6: # stopping condition
    print("Number", a, "reached")
    break # this will break loop
  elif a < 6: # if less, than add 2
    a = a + 2
    print("Adding 2... Reached", a)
    continue # returning to loop start
  else: # if greater, then subtract 1
    a = a - 1
    print("Subtracting 1... Reached", a)
    continue # returning to loop start

Task

Using while loop and continue/break commands construct the next program:

Task

Using while loop and continue/break commands construct the next program:

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Section 6. Chapter 2

while loop (2/2)

For example, imagine we have number 3 and want to reach number 6. All we can do - is to add 2 and subtract 1.


              12345678910111213141516
            
# starting number
a = 3

# let's construct while loop
while True: # infinite loop
  if a == 6: # stopping condition
    print("Number", a, "reached")
    break # this will break loop
  elif a < 6: # if less, than add 2
    a = a + 2
    print("Adding 2... Reached", a)
    continue # returning to loop start
  else: # if greater, then subtract 1
    a = a - 1
    print("Subtracting 1... Reached", a)
    continue # returning to loop start

Task

Using while loop and continue/break commands construct the next program:

Task

Using while loop and continue/break commands construct the next program:

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

For example, imagine we have number 3 and want to reach number 6. All we can do - is to add 2 and subtract 1.


              12345678910111213141516
            
# starting number
a = 3

# let's construct while loop
while True: # infinite loop
  if a == 6: # stopping condition
    print("Number", a, "reached")
    break # this will break loop
  elif a < 6: # if less, than add 2
    a = a + 2
    print("Adding 2... Reached", a)
    continue # returning to loop start
  else: # if greater, then subtract 1
    a = a - 1
    print("Subtracting 1... Reached", a)
    continue # returning to loop start

Task

Using while loop and continue/break commands construct the next program:

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Section 6. Chapter 2

Switch to desktop for real-world practiceContinue from where you are using one of the options below