Python Basics#

Here are some quick examples to refresh your understanding of Python code.

This is not meant to be a comprehensive tutorial.

We encourage you to explore ProjectPythia for additional Python resources and tutorials.

Please run these examples demonstrated today yourself!#

  • Press Shift+Enter to execute each code cell!

  • Feel free to make changes and explore!

Starting off - Hello World!#

print("Hello World!")
print('Hello Students!')

Loops#

  • for loops are a staple of scientifc programming.

for i in range(10):
    print(i)

Things to Note:#

  • Python defaults to counting starting from 0 rather than 1.

  • Function calls (such as range) always use parentheses.

  • for loops require colons as punctuation to start.

  • Code blocks are indicated through indentations.

    • NOTE indentations need to be similar for each block of code.

print('start of loop')
for i in range(10):
    print('in loop')
print('outside of loop')

Program Control - Conditional Statements#

For logical decisions, Python has an if statement

if i > 2: 
    print("i is greater than 2!")
else:
    print("i is less than 2!")

QUESTION Why is i greater than 2? What value is i? If you do not know, how could you determine the value?

Python also defines True and False logical conditions

i < 8

Python also includes compound statements and and or

for i in range(10):
    if i > 2 and i <= 8:
        print(f"this is iteration number {i}.")
    if i > 9 or i < 0:
        print('this condition is never met')

Things to Note:#

  • if statements can also use less than or equal to notation <=

  • The and statement uses formatted output

Basic Python Data Types#

A key strength of Python are the flexible data types, the core of which are noted below

QUESTION What data type is i?

print(type(i))

Floating Point Numbers float#

a = 10.58
b = 1e-9
print(a, type(a))
print(b, type(b))

Things to Note:#

  • print statements can take multiple inputs

  • float numbers are include scientific notation

Character strings str#

As we have been doing, you can use either single quotes '' or double quotes "" to denote strings

c = 'Argonne National Laboratory'
d = "Atmospheric Sciences" 
e = "cloudy, hot, humid"

print(c)
print(d)
print(e)
print(type(c), type(d), type(e))

Lists#

  • A ordered container of objects denoted by square brackets

  • Note that objects can be any data type

mylist = [10, 20, 30, 40]

print(mylist, type(mylist))

Things to Note:

  • you can also iterate through lists

  • lists do not need to contain the same type of data!

newlist = [10, 20.5, 1e9, 'Python']
for var in newlist:
    print(var, type(var))

  • Since Lists are ordered we can access items by index

newlist[1]

What Now?#

  • Now that the Python basics have been reintroduced, let’s take a look a specific libraries that are useful in scientific applications

Matplotlib - Scientific Data Visualization#

From the Matplotlib Documentation:

Matplotlib is a comprehensive library for creating static, animated, and interactive visualizations in Python. Matplotlib makes easy things easy and hard things possible.

  • Create publication quality plots.

  • Make interactive figures that can zoom, pan, update.

  • Cus tomize visual style and layout.

  • Export to many file formats.

  • Embed in JupyterLab and Graphical User Interfaces.

  • Use a rich array of third-party packages built on Matplotlib.

Additional Tutorials:

# Data we wish to display
varA = [0, 1, 2, 3, 4]
varB = [0, 1, 2, 3, 4]
varC = [0, 1, 4, 9, 16]

import matplotlib.pyplot as plt # Convention is to import and rename. Best to stick with convention

# Create a Figure
fig = plt.figure()

# Add an axis to display data in
ax = fig.add_subplot(1, 1, 1)

# Plot the first set of data
ax.plot(varA, varB, label='y = x') # include a label!
# Plot the second set of data
ax.plot(varA, varC, label=r'y = x$^2$')
# Label your axes
ax.set_ylabel('Y Values [#]')
ax.set_xlabel('X Values [#]')
# Add a title
ax.set_title('First Matplotlib Plot')
# Add a legend
ax.legend(loc='upper left')
# Display!
plt.show()

Resources and References#