파이썬 while for - paisseon while for

In programming, loops are used to repeat a block of code. For example, if we want to show a message 100 times, then we can use a loop. It's just a simple example, we can achieve much more with loops.

In the previous tutorial, we learned about Python for loop. Here, we are going to learn about

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

Python

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

The syntax of

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

while condition:
    # body of while loop

Here,

1. A

   # program to display numbers from 1 to 5
   
   # initialize the variable
   i = 1
   n = 5
   
   # while loop from i = 1 to 5
   while i <= n:
       print(i)
       i = i + 1

   0 loop evaluates the

   # program to display numbers from 1 to 5
   
   # initialize the variable
   i = 1
   n = 5
   
   # while loop from i = 1 to 5
   while i <= n:
       print(i)
       i = i + 1

   4
2. If the

   # program to display numbers from 1 to 5
   
   # initialize the variable
   i = 1
   n = 5
   
   # while loop from i = 1 to 5
   while i <= n:
       print(i)
       i = i + 1

   4 evaluates to

   # program to display numbers from 1 to 5
   
   # initialize the variable
   i = 1
   n = 5
   
   # while loop from i = 1 to 5
   while i <= n:
       print(i)
       i = i + 1

   6, the code inside the

   # program to display numbers from 1 to 5
   
   # initialize the variable
   i = 1
   n = 5
   
   # while loop from i = 1 to 5
   while i <= n:
       print(i)
       i = i + 1

   0 loop is executed.

3. # program to display numbers from 1 to 5
   
   # initialize the variable
   i = 1
   n = 5
   
   # while loop from i = 1 to 5
   while i <= n:
       print(i)
       i = i + 1

   4 is evaluated again.
4. This process continues until the condition is

   # program to display numbers from 1 to 5
   
   # initialize the variable
   i = 1
   n = 5
   
   # while loop from i = 1 to 5
   while i <= n:
       print(i)
       i = i + 1

   9.
5. When

   # program to display numbers from 1 to 5
   
   # initialize the variable
   i = 1
   n = 5
   
   # while loop from i = 1 to 5
   while i <= n:
       print(i)
       i = i + 1

   4 evaluates to

   # program to display numbers from 1 to 5
   
   # initialize the variable
   i = 1
   n = 5
   
   # while loop from i = 1 to 5
   while i <= n:
       print(i)
       i = i + 1

   9, the loop stops.

Flowchart for Python While Loop

Example: Python while Loop

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

Output

1
2
3
4
5

Here's how the program works:

VariableCondition:

1
2
3
4
5

1
2
3
4
5

1
2
3
4
5

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

1
2
3
4
5

1
2
3
4
5

1
2
3
4
5

1
2
3
4
5

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

current_level = 0
final_level = 5

game_completed = True

while current_level <= final_level:
    if game_completed: 
        print('You have passed level', current_level)
        current_level += 1

print('Level Ends')

1
2
3
4
5

current_level = 0
final_level = 5

game_completed = True

while current_level <= final_level:
    if game_completed: 
        print('You have passed level', current_level)
        current_level += 1

print('Level Ends')

1
2
3
4
5

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

current_level = 0
final_level = 5

game_completed = True

while current_level <= final_level:
    if game_completed: 
        print('You have passed level', current_level)
        current_level += 1

print('Level Ends')

1
2
3
4
5

current_level = 0
final_level = 5

game_completed = True

while current_level <= final_level:
    if game_completed: 
        print('You have passed level', current_level)
        current_level += 1

print('Level Ends')

1
2
3
4
5

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

You have passed level 0
You have passed level 1
You have passed level 2
You have passed level 3
You have passed level 4
You have passed level 5
Level Ends

1
2
3
4
5

You have passed level 0
You have passed level 1
You have passed level 2
You have passed level 3
You have passed level 4
You have passed level 5
Level Ends

1
2
3
4
5

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

You have passed level 0
You have passed level 1
You have passed level 2
You have passed level 3
You have passed level 4
You have passed level 5
Level Ends

1
2
3
4
5

You have passed level 0
You have passed level 1
You have passed level 2
You have passed level 3
You have passed level 4
You have passed level 5
Level Ends

1
2
3
4
5

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

Example 2: Python while Loop to Display Game Level

current_level = 0
final_level = 5

game_completed = True

while current_level <= final_level:
    if game_completed: 
        print('You have passed level', current_level)
        current_level += 1

print('Level Ends')

Output

You have passed level 0
You have passed level 1
You have passed level 2
You have passed level 3
You have passed level 4
You have passed level 5
Level Ends

In the above example, we have used the

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

Infinite while Loop in Python

If the

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

# infinite while loop
while True:
    # body of the loop

In the above example, the

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

Python While loop with else

A

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

# infinite while loop
while True:
    # body of the loop

The

# infinite while loop
while True:
    # body of the loop

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

counter = 0

while counter < 3:
    print('Inside loop')
    counter = counter + 1
else:
    print('Inside else')

Output

Inside loop
Inside loop
Inside loop
Inside else

Here, we have used the counter variable to print the

counter = 0

while counter < 3:
    print('Inside loop')
    counter = counter + 1
else:
    print('Inside else')

On the fourth iteration, the condition in

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

# program to display numbers from 1 to 5

# initialize the variable
i = 1
n = 5

# while loop from i = 1 to 5
while i <= n:
    print(i)
    i = i + 1

# infinite while loop
while True:
    # body of the loop