1. Python workshop
Marc Tavenier –

2. Contents Why use Python in our field? The basics
Working with Excel data
Plotting
How to use Google if you’re stuck
2 practical assignment
Python workshop

3. Why use Python in our field?
1/24/2020
Why use Python in our field?
Way more versatile
The number 2 most popular programming language (behind JavaScript, which is way more difficult for beginners)
Completely free
Platform-agnostic
What are we aiming to substitute? Python is better than Excel, R and Matlab at dealing with tabular data.
Python workshop

4. Getting started – the basics
Environment
Language
Control Flow
Organizing
Libraries
Python workshop

5. Environment Anaconda Navigator Spyder Python workshop 1/24/2020
Anaconda = toolset for data scientists
Spyder = one of those tools that is a scientific python development environment
Python workshop

6. 56 3 1003 56.1 3.001 TRUE FALSE ”Richard Mollier” [1, 2, 3, “Richard”]
1/24/2020
Language
Booleans
Integers = ℤ
Floats = ℝ
Strings
Lists
Tuples
TRUE FALSE
”Richard Mollier”
[1, 2, 3, “Richard”]
(1, 2, 3, “Richard”)
Lists = mutable; can be modified after creation
Tuples = immutable; can not be modified after creation.
Usually lists are the better way to go.
Python workshop

7. 1/24/2020
Control Flow
“ IF my master project is not complete within one year, choose another study.”
if master_project is not complete:
choose_another_study = True
elif study_duration > 10: #years
just_quit = True
else:
print("You're winning in life")
Does anyone know what type of variable complete is?
Python workshop

8. Iterate over a sequence (list, tuple, string, etc.)
1/24/2020
Control Flow
“ FOR … ”
Iterate over a sequence (list, tuple, string, etc.)
chairs = ["Performance", "Materials", "Lighting"]
for chair in chairs:
print(chair)
Using the ‘for-loop’ we can iterate over a sequence. A sequence can be a list, a tuple, a string, etc.
Python workshop

9. Execute a set of statements as long as a condition is True
1/24/2020
Control Flow
“ WHILE … ”
Execute a set of statements as long as a condition is True
i = 1
while i < 5:
print(i) i = i + 1
With the while loop we can execute a set of statements as long as a condition is True. Do make sure that the condition will turn True at some point, or you have yourself an infinite loop.
i += 1
Python workshop

10. Organizing def function_1(x, y): # insert plot script here
1/24/2020
Organizing
def function_1(x, y):
# insert plot script here
function_1(x=1, y=2)
”””
leave a slightly longer message
for your future self
chairs = ["Performance", "Materials"]
for chair in chairs:
print(chair)
# leave a message for your future self #
chairs = ["Performance", "Materials"]
for chair in chairs:
print(chair)
Line comments
Block comments
Function definition
def function_2(x, y):
z = x * y
return z
z = function_2(x=1, y=2)
Python workshop

11. Libraries Pandas Numpy Matplotlib Communication with Excel
1/24/2020
Libraries
Pandas
Communication with Excel
Data management:
Alignment
Reshaping
Pivoting
Merging
Numpy
MATLAB-like operations that can be done on arrays or matrices
Nd-array: n-dimensional array / data structure
Matplotlib
MATLAB-like plotting library
Python workshop

12. Working with Excel data
1/24/2020
Working with Excel data
import pandas as pd df = pd.read_excel('file.xlsx', sheet_name='Data’) mean_value = df.mean() min_value = df.min() max_value = df.max() print(mean_value) print(min_value) print(max_value)
Python workshop

13. Plotting Plots you can’t (easily) make with Excel: Boxplots
1/24/2020
Plotting
Plots you can’t (easily) make with Excel:
Boxplots
Violin plots
Scatter plots filtered via colour/marker size
Contour plots
Vector plots
Heatmaps
Polar plots
Etc.
Python workshop

14. 1/24/2020
Plotting
import matplotlib.pyplot as plt plt.plot([1, 2, 3, 4]) plt.ylabel('some numbers’) plt.show()
Smallest code example
Python workshop

15. How to Google What not to do: What to do instead:
1/24/2020
How to Google
What not to do:
“ My plot won’t plot why ”
What to do instead:
Try the cheat sheets if you’re a beginner
Include “Python” in the search to make sure you’re not looking at a different language
Use proper terminology
Copy paste the Python error, click search and watch the magic happen.
Conclusion and jokes for the lulz
Python workshop

16. Practical assignment Time to whip out your laptops! Assignment 1:
1/24/2020
Practical assignment
Time to whip out your laptops!
Assignment 1:
Use energy.xlsx to create a correlation matrix
Tips:
Calculate the correlations with Pandas
Use the matshow function from Matplotlib
Python workshop

17. Practical assignment import matplotlib.pyplot as plt
How I did it:
import matplotlib.pyplot as plt
import pandas as pd
df = pd.read_excel('energy.xlsx')
corr = df.corr()
plt.matshow(corr)
plt.show()
Python workshop

18. Practical assignment Time to whip out your laptops! Assignment 2:
1/24/2020
Practical assignment
Time to whip out your laptops!
Assignment 2:
Use co2.xlsx to create a boxplot or violin plot per measurement
Make it a plot usable for a report, so don’t forget the necessary labels
Python workshop

19. Practical assignment How I did it: import pandas as pd
import matplotlib.pyplot as plt
# load Excel
df = pd.read_excel('co2.xlsx', header=0)
# create figure
fig, ax = plt.subplots()
# transpose data
df = df.T
# make boxplot
ax.boxplot(df)
# style boxplot
ax.set_title('$CO_2$ measurements’)
ax.set_ylabel('$CO_2$ concentration (ppm)’)
# show plot
plt.show()
Practical assignment
How I did it:
Python workshop

20. Practical assignment Assignment 3: Use pv.xlsx to create an RMSE plot
1/24/2020
Practical assignment
Assignment 3:
Use pv.xlsx to create an RMSE plot
Make it a plot usable for a report, so don’t forget the necessary labels
Bonus points if you add an x=y line
Super bonus points if you add a color bar
Python workshop

21. Practical assignment
How I did it:
Python workshop

22. import matplotlib.pyplot as plt # import Excel
import pandas as pd
import matplotlib.pyplot as plt
# import Excel
df = pd.read_excel('pv.xlsx', header=0, index_col=0)
# get values from DataFrame
meas = df['Measurement’]
sim = df['Simulation’]
days = df.index.values
# make plot
fig, ax = plt.subplots()
ax.scatter(x=meas, y=sim, c=days)
# style plot
ax.set_title('RMSE plot’)
ax.set_xlabel('Measured irradiance ($Wh/m^2$)’)
ax.set_ylabel('Simulated irradiance ($Wh/m^2$)’)
ax.set_xlim(left=0, right=9000)
ax.set_ylim(bottom=0, top=9000)
ax.plot([0, 1], [0, 1], transform=ax.transAxes, zorder=0, color='gray')
Python workshop

23. import matplotlib as mpl import numpy as np
# create colorbar
import matplotlib as mpl
import numpy as np
norm = mpl.colors.Normalize(vmin=0, vmax=365)
sm = plt.cm.ScalarMappable(norm=norm)
sm.set_array([])
cbar = plt.colorbar(sm, ticks=np.linspace(0, 360, 10), boundaries=np.arange(0, 365, 1))
cbar.ax.set_ylabel('Day of the year', rotation=-90, va='bottom’)
# show plot
plt.show()
Python workshop

24. Thanks for joining!
Marc Tavenier –

25. 1/24/2020
Useful resources
Matplotlib example gallery:
More on Python basics:
The scripts of today
The handed-out cheat sheets
Python workshop