#!/usr/bin/env python
# coding: utf-8

# # while loops
# 
# The **while** statement in Python is one of most general ways to perform iteration. A **while** statement will repeatedly execute a single statement or group of statements as long as the condition is true. The reason it is called a 'loop' is because the code statements are looped through over and over again until the condition is no longer met.
# 
# The general format of a while loop is:
# 
#     while test:
#         code statement
#     else:
#         final code statements
# 
# Let’s look at a few simple while loops in action. 

# In[2]:


x = 0

while x < 10:
    print 'x is currently: ',x
    print ' x is still less than 10, adding 1 to x'
    x+=1


# Notice how many times the print statements occurred and how the while loop kept going until the True condition was met, which occurred once x==10. Its important to note that once this occurred the code stopped. Lets see how we could add an else statement:

# In[3]:


x = 0

while x < 10:
    print 'x is currently: ',x
    print ' x is still less than 10, adding 1 to x'
    x+=1
    
else:
    print 'All Done!'


# #break, continue, pass
# 
# We can use break, continue, and pass statements in our loops to add additional functionality for various cases. The three statements are defined by:
# 
#     break: Breaks out of the current closest enclosing loop.
#     continue: Goes to the top of the closest enclosing loop.
#     pass: Does nothing at all.
#     
#     
# Thinking about **break** and **continue** statements, the general format of the while loop looks like this:
# 
#     while test: 
#         code statement
#         if test: 
#             break
#         if test: 
#             continue 
#     else:
# 
# **break** and **continue** statements can appear anywhere inside the loop’s body,but we will usually put them further nested in conjunction with an **if** statement to perform an action based on some condition.
# 
# Lets go ahead and look at some examples!

# In[6]:


x = 0

while x < 10:
    print 'x is currently: ',x
    print ' x is still less than 10, adding 1 to x'
    x+=1
    if x ==3:
        print 'x==3'
    else:
        print 'continuing...'
        continue


# Note how we have a printed statement when x==3, and a continue being printed out as we continue through the outer while loop. Let's put in a break once x ==3 and see if the result makes sense:

# In[7]:


x = 0

while x < 10:
    print 'x is currently: ',x
    print ' x is still less than 10, adding 1 to x'
    x+=1
    if x ==3:
        print 'Breaking because x==3'
        break
    else:
        print 'continuing...'
        continue


# Note how the other else statement wasn't reached and continuing was never printed!
# 
# After these brief but simple examples, you should feel comfortable using while statements in you code.
# 
# **A word of caution however! It is possible to create an infinitely running loop with while statements. For example:**

# In[ ]:


# DO NOT RUN THIS CODE!!!! 
while True:
    print 'Uh Oh infinite Loop!'


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