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

# This is the transcript of the lecture material from Friday, November 15, 2024.<br>
# <br>
# Let's start by building two collections that look like arrays in Fortran.  Notice the difference in notation between a and b, however.<br>
# Collection a uses ()'s, while b uses []'s.

# In[1]:


a = (2,3,4)
b = [2,3,4]


# Let's see what each one of these really is.

# In[2]:


type(a)


# In[3]:


type(b)


# Collection a is a tuple, while collection b is a list.  What is the difference?  Let's start by changing an element of list b.

# In[4]:


b[1] = 5


# In[5]:


print(b)


# Ok.  No problem.  This worked.  Notice that b[1] is the SECOND element of the list.  Remember, python indexing starts with 0, not 1 like Fortran.<br>
# Great.  Now let's try and change an element of tuple a.

# In[6]:


a[1] = 5


# We get an error.  Why?  The reason is that lists are mutable (able to be changed), and tuples are immutable (not able to be changed).<br>
# When we tried to change an element of the tuple, python threw an error.<br>
# Let's look at another list.

# In[7]:


b = [91, 'Lions', 273.15]


# In[8]:


type(b[0])


# In python, lists and tuples can contain elements of different types.  Our new list b contains an integer, string, and float.<br>
# What happens with this line?

# In[9]:


print(a[3])


# We get an error because we are trying to reference and element that is outside of the defined range.<br>
# Tuple a contains three things (2,3,4), but you reference them through a[0], a[1], a[2].  The valid indices are 0, 1, and 2.  Not 3.<br><br>
# Let's look at another feature of python.  Here is a new list.

# In[10]:


a = ['Lions', 'Tigers', 'Bears']


# Now, let's set list b equal to a and verify that the command worked.

# In[11]:


b = a


# In[12]:


print(a,b)


# Great.  Everything looks good.  Now, let's change the second element (index 1) of list a and print out our lists again.

# In[13]:


a[1] = 'Bananas'


# In[14]:


print(a,b)


# What happened?  Both list a and list b changed.  This is because the statement b=a is what is called a "soft copy."<br>
# This is often not desireable.  What do we do?  We make something called a "hard copy."

# In[15]:


c = a[:]


# In[16]:


print(a,b,c)


# In[17]:


a[1] = 'Apples'


# In[18]:


print(a,b,c)


# c = a[:] is called a "hard copy" and notice when we change list a again, b changed, but c didn't.<br>
# The reason is that list c is a "hard copy" of list a and list b is a "soft copy" of list a.<br><br>
# Ok, let's move on to something else.

# In[19]:


import numpy as np
import matplotlib.pyplot as plt


# These two lines import two packages from the python libraries.<br>
# Notice the use of np and plt as aliases to the numpy and matplotlib packages.

# In[20]:


x = np.linspace(-2,2,200)


# The line above creates a list of numbers from -2 to 2 with 200 equally spaced points.<br>
# Let's print the list to understand it bettter.

# In[21]:


print(x)


# Now that we have the list, let's do something cool with it like make a plot.

# In[22]:


plt.plot(x,x**2, color="red")
plt.xlabel('x')
plt.ylabel('y')
plt.title("$y = x^2$", fontdict={'size':22})


# The code in the box above creates a plot of x^2, labels the x and y axis, and gives the plot a title.<br>
# Feel free to play around with this.  Change the plot color, the size of the title, etc.

# In the next cells, I create a new list and print the list for verification.<br>
# This should look familiar.

# In[23]:


mylist = [91, 13, 5, 19, 9]


# In[24]:


print(mylist)


# Examine the following code.  This is an example of a loop structure in python.

# In[25]:


for item in mylist:
    print(item)


# What this does is go through each element in the list mylist, place that element of the list into<br>
# the variable item and then prints the variable.  Notice that each element in the list is printed separately.<br><br>
# We can take this another step with the following code.  Look it over and make sure you understand it.

# In[26]:


for item in mylist:
    print(item, item**2, item**3)
    # I could also do more here.  It doesn't need to be just one line.


# Also note the use of an inline comment in python using the hashtag.

# The following code uses the range function to create a list and prints out the items of the list.<br>
# Notice it only goes from 1 to 10.<br>

# In[27]:


for i in range(1,11):
    print(i)


# See if you understand the output from the following code.

# In[28]:


for i in range(4,8,2):
    print(1)


# Ok, I fooled you a bit there, but you should still understand the output.<br>
# The code below is what you were expecting and the output.

# In[29]:


for i in range(4,8,2):
    print(i)