|
 |
|
SDA intros
|
|
|
|
|
Questions
|
|
|
|
|
Get to know you activity
|
|
|
 |
|
Refresh
|
|
|
|
|
arithmetic operators
|
|
|
|
|
variable name on left side vs right side
|
|
|
|
|
to make variable names easier to read, convention is to use underscores or capitalization
|
|
|
|
|
cur_temp or curTemp
|
|
|
|
|
the former is called snake case and the latter is called camel case
|
|
|
|
|
what might make for a good variable name?
|
|
|
|
|
not too long
|
|
|
|
|
describes what the variable represents
|
|
|
|
|
Problem: what icon to display in weather app?
|
|
|
|
|
Simplified problem: difference between current and “hot” temperature (i.e., should the app show the current temperature in red)
|
|
|
|
|
calculate difference
|
|
|
|
|
difference = hot_temp - cur_temp_F
|
|
|
|
|
make a diagram of memory after each step (line of code)
|
|
|
|
|
diagram the following steps
|
|
|
|
|
x = 10
y = x
x = x + 5
|
|
|
|
|
y and x label separate locations in memory, the second step copies the value stored as x to a new location and labels it y
|
|
|
|
|
so the third line overwrites the value for x, but not for y
|
|
|
|
|
[NOW ON SCREEN] output result (three mistakes: missing “, missing ), typo in variable name)
|
|
|
|
|
Forgetting a close “ around text causes a SyntaxError
|
|
|
|
|
anatomy of the error message
|
|
|
|
|
File where the error occurred, line where the error occurred, and the error type and message
|
|
|
|
|
it may feel like it’s Python yelling at you for your mistakes
|
|
|
|
|
really Python catching on fire and saying “I don’t understand, aaaaaaaahhhhhhhhhh.”
|
|
|
|
|
how would you demonstrate to me this is correct (or incorrect)
|
|
|
|
|
print everything, check for known results
|
|
|
|
|
compare to one-line version
|
|
|
|
|
print(“difference between hot and current temp in Celsius:”, (80 - 32) / 9 * 5 - get_cur_temp())
|
|
|
|
|
comments
|
|
|
|
|
any line that starts with a # is a comment
|
|
|
|
|
ignored by Python, useful for explaining and documenting your code
|
|
|
|
|
Python Standard Library
|
|
|
|
|
https://docs.python.org/3/library/index.html
|
|
|
|
|
Made up of modules which are made available by importing them
|
|
|
|
|
example
|
|
|
|
|
import math
print(math.sqrt(100)) # prints 10
print(math.sqrt(-100)) # causes ValueError since sqrt doesn’t know how to handle negative numbers
|
|
|
|
|
Note how we access sqrt by writing <module name>.sqrt, this is how modules work in general
|
|
|
|
|
Variation on import
|
|
|
|
|
from math import sqrt
|
|
|
|
|
lets us just write sqrt instead of math.sqrt
|
|
|