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

# # Module 2
# 
# ## Video 5: Program Flow II
# **Python for the Energy Industry**
# 
# ## Conditionals

# The `if` statement allows you to specify what to do if a condition is true. Let's say you also want to specify what to do if it is not true:

# In[1]:


vessel = "ROCINANTE"

if vessel == "QUIXOTE":            
    print('Vessel is named QUIXOTE')
    
else:
    print('Vessel is named something else')  


# Multiple conditions can be checked for using `elif` and `else`. These must immediately follow an `if` statement. `elif` will run the indented code if the previous condition is not true, but some other specified condition is true. `else` will always run if the previous condition is not true.

# In[4]:


vessel = "DON"

if vessel == "QUIXOTE":            
    print('Vessel is named QUIXOTE')
    
elif vessel == "ROCINANTE":
    print('Vessel is named ROCINANTE')
    
elif vessel == "DON":
    print('Vessel is named DON')
    
else:
    print('Vessel is named something else')  


# In this example, the first check is if the vessel name is 'QUIXOTE'. As it is not, a second check is done to see if the name is 'ROCINANTE'. This is true, so no further check is done. 

# ## Loops
# 
# A loop is used to run a chunk of code multiple times. The number of times may be specified in advance, or it may depend on some condition being true, such as in this example of a `while` loop:

# In[5]:


my_num = 0

while my_num < 5:
    my_num = my_num + 1
    print('my_num =',my_num)
    
print('done')


# In[6]:


my_num = 1
my_sum = 0

while my_num <= 10:
    my_sum = my_sum + my_num
    my_num += 1
    
print(my_sum)


# Here the indented code will run over and over, until the condition that `my_num` is less than 5 is no longer true. Because the indented code adds 1 to `my_num` each time, the code block only runs 5 times. Be careful: if you'd forgotten to change the value of `my_num` within the indented code block, the loop would keep on running until you force it to stop!

# ### For Loops
# 
# A `for` loop is a type of loop which iterates over a number of items. For loops are often paired with `range` to iterate over successive numbers:

# In[10]:


for x in range(3):
    print(x)


# The usefulness of `for` loops will become more clear in the next video.

# ### Exercise:
# Use a `for` loop to print the sum of all numbers up to and including 100. You should get 5050.

# In[ ]: