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Learn Python from Scratch
course content

Course Content

Learn Python from Scratch

Learn Python from Scratch

1. The basics
Hello, World!Hello, me!VariablesCommentsIndentationNumbers and strings
2. Arithmetic operations
AdditionMultiplication and powerDivision and whole part division
3. Common data types
Data typesNumbersfloat and intStoring textStrings slicingConcatenation
4. Conditional statements
Boolean data typeCombining conditionsSimple 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 functionsWriting 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

bookwhile 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
copy

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.

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Section 6. Chapter 2
toggle bottom row

bookwhile 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
copy

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.

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Everything was clear?

How can we improve it?

Thanks for your feedback!

Section 6. Chapter 2
toggle bottom row

bookwhile 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
copy

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.

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Everything was clear?

How can we improve it?

Thanks for your feedback!

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
copy

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.

Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
Section 6. Chapter 2
Switch to desktopSwitch to desktop for real-world practiceContinue from where you are using one of the options below
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