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

# # For loop exercises

# In[1]:


import numpy as np


# You may remember you can print a number (or anything else) with the `print` function, like this:

# In[2]:


print(5)


# Use a `for` loop to print out all the numbers from 3 through 7, one number on each line.

# In[3]:


# Your code here.


# Make an empty list called `my_list`.  Use a `for` loop to append all the numbers between 0 and 10 (inclusive) to `my_list`.  Show the list at the end of the loop.

# In[4]:


# Your code here.
my_list = []


# Make a new variable `total` equal to 0. Use a `for` loop to add all the
# numbers from 15 through 32 to `total`.  Print the value at the end of the loop.
# 
# Hint - here is a statement where I add 10 to the variable
# `my_variable`: `my_variable = my_variable + 10`.

# In[5]:


# Your code here.
total = 0


# Use a `for` loop to add up all the even numbers from -102 through 98.
# Hint: you may like to use the `step` argument.

# In[6]:


# Sum of all even numbers from -102 through 98.
total = 0


# Have a look at the definition of the
# [factorial](https://en.wikipedia.org/wiki/Factorial).
# 
# For example, the factorial of 5, written $5!$ is `1 * 2 * 3 * 4 * 5`.
# 
# Use a `for` loop to calculate $15!$.  Print out the result.
# 
# Note: those of you on Windows will have to start with a floating point
# value \- as in `factorial = 1.0` \- in order to avoid a nasty
# interaction between Numpy, Windows, and integers.

# In[7]:


# Calculate 15!
# Note the floating point number to start.
factorial = 1.0


# These are getting a bit harder.

# You can break out of a `for` loop using the `break` statement.  Here
# I break out of the `for` loop, when I get to 6.  Notice I never get to
# 7 or any number higher than 6.  The `break` statement says, "stop the
# `for` loop now, and go directly to the first statement after the `for`
# loop".

# In[8]:


for i in np.arange(1000):
    print(i)
    if i == 6:
        print("Stopping here, where i == 6")
        break
print("I have finished the for loop now.")


# Make sure you understand what is going on in the cell above.  When you
# do, try using this technique to find the largest integer $n$ where $n!
# < 10^6$.  Print out $n$ and $n!$.  Hint for your `for` loop: $n$ is
# less than 100.

# In[9]:


factorial = 1
last_factorial = 1
threshold = 1000000
# Your code here


# Here is an array of 50 numbers:

# In[10]:


# Run this cell to define the "values" array
values = np.array([ 3,  32,  39, -3,  34,  28,   9,  36,
         -4,  20,  -4,  13,  32,  9,  14, 999,   2,  20,  18,
         12,  13,  25,  25,   2,  17,  39, 39,   4,  26,   7,
          1,  36,  31,  15,  25,  19, 999, -4,  -3,  24,   7,
         14,  -2,  35,  18,  23,  34,  14, 11,  25])


# Add up all the numbers in this array, until you get to the first value
# of 999.  Print the sum of all the values up to, but not including, the
# first 999. For example, if the array was `np.array([2, 6, 4, 999,
# 11])`, then the result would be: `2 + 6 + 4 == 12`.
# What is the equivalent result for the `values` array above?

# In[11]:


# Your code here.


# The next cell is a slight variation.  Add all the numbers in this
# array, up to, but not including, the first value of 999.  This time,
# discard any negative values you find.  For example, if the array was
# `np.array([1, 7, -3, 4, 999, 13])`, then the result would be:
# `1 + 7 + 4 == 12`.
# What is the equivalent result for the `values` array above?

# In[12]:


# Your code here.