28  While

28.1 First example

while condition_is_true:
    do_something
a = 0            
while a < 10:
    a = a + 1
    print(a)

When you use while loops, you need to first initialize your loop variable, and you need to also modify that variable so that loop will finish at some time.

28.2 No initialization example

    while x < 10: 
        print(x)

Output will be like below.

    while x < 10: 
        print(x) 
NameError                                 Traceback (most recent call last)
<ipython-input-1-c956f313d152> in <module>
----> 1 while x < 10:
      2     print(x)

NameError: name 'x' is not defined

28.3 infinite loop

Not modifying condition variable. Following code will be infinite loops of 1 until you close the program or use CTRL-c.

x = 1
while x < 10: 
    print(x)

correct solution should be.

x = 1
while x < 10: 
    print(x) 
    x = x +1

28.5 Video Tutorials