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from IPython.display import HTML
import requests
HTML(requests.get("https://git.io/fh5WI").text)
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Python and Jupyter for Programmers
Part 1: Jupyter and Python Basics
Contents
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1. Jupyter Notebook and JupyterLab
Jupyter Notebook (used in this workshop)
- Has been around since 2011.
- Works with one notebook file at a time.
Jupyter Lab
- Eventual successor to Jupyter Notebook.
- The same basic functionality as the Notebook, but more flexible environment - can work with multiple notebooks/files side by side.
- Still in beta.
- Works fine most of the time, but some notebook functionality not quite there yet.
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3*5
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print("hello!")
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2+3
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2*3
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2**3
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2.0*3.0
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Integers can be of an arbitrary size:
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2**10000
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Size of floats is limited:
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2.0**10000
Modulus:
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19%5
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20%5
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a = 3
b = 4
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a+b
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a,b,c = 4, 5, 6
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a
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b
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c
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a, b
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a, b = b, a
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a, b
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3.3 Importing Modules
Built-in functionality of Python is limited. E.g. no trigonometric functions:
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sin(0)
Good news: There are external libraries (modules) suited for almost any task.
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import math
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dir(math)
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help(math)
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math.pi
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math.sin(math.pi)
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More convenient ways to import:
1. Give a module a nickname:
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import math as m
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m.sin(m.pi)
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2. Import some module content directly:
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from math import sin, pi
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sin(pi)
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3. Import the whole module content directly (not recommended):
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from math import *
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cos(pi)
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log(pi)
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a = 'Hello'
print(a)
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b = "world!"
print(b)
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c = '''more than
one line'''
print(c)
String concatenation:
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c = a + b
print(c)
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print(10*a)
f-strings:
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a = 1
b = 2
c = a + b
s = f"{a} plus {b} equals {c}"
print(s)
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Note: In Python code blocks are defined by their indentation.
3.5 if/then/else
if condition:
do this
do this
do this
else:
do this
do this
Note: In Python code blocks are defined by their indentation.
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x = 101
if x > 100:
print('big number')
print('Done!')
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x = 0
if x > 100:
print("big number")
else:
print("small number")
print("Done!")
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10 > 5
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10 == 5
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10 != 5
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(10 > 5) or (10 < 5)
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(10 > 5) and (10 < 5)
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Note:
- Non-zero numbers and non-empty strings are interpreted as
True. - Zero and an empty string give
False.
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x = 7
if x:
print("Yes!")
else:
print("No!")
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i = 1
while i < 5:
print(i*10)
i += 1
print("Done!")
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r = input("Delete file? (yes/no): ")
while True:
if r == 'no':
print("Cancelled")
break
elif r == 'yes':
print("File deleted")
break
else:
print(f'invalid option: "{r}"')
r = input("Delete file? (yes/no): ")
- A list is an ordered collection of objects of arbitrary types.
- It is created by enclosing objects in square brackets:
mylist = [a, b, c]
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mylist = [3, 5.1, "Hello", True]
mylist
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for x in mylist:
print(2*x)
Note:
For all practical purposes True and False are the same as 1 and 0:
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True == 1
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False == 0
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Accessing list items (indexing starts at 0):
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mylist
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mylist[0]
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mylist[2]
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Negative indexing counts from the end:
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mylist[-1]
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mylist[-2]
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List concatenation:
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x = [1, 2, 3] + ['a', 'b', 'c']
x
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Appending an element to a list:
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x
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x.append('Hello')
x
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3.9 Lists Slicing
- Creates a sublist of a list.
mylist[start : stop]
mylist[start : stop : step]
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numbers = list(range(20))
numbers
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numbers[5:15]
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numbers[5:15:3]
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Strings can be sliced too:
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s = "University at Buffalo"
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s[4:16]
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s[::2]
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3.10 Lists Comprehensions
- Creates a new list from a given list.
[f(x) for x in mylist]
[f(x) for x in mylist if condition]
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numbers = list(range(10))
numbers
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squares = [x**2 for x in numbers]
squares
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even_squares = [x**2 for x in numbers if x%2 == 0]
even_squares
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The same with the "for" loop:
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even_squares2 = []
for x in numbers:
if x%2 == 0:
even_squares2.append(x**2)
even_squares2
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Example: FizzBuzz
Write a program that prints the numbers from 1 to 100. But:- for multiples of 3 print “Fizz” instead of the number
- for the multiples of 5 print “Buzz”
- for multiples of both 3 and 5 print “FizzBuzz”.
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fb = [("Fizz" if x%3==0 else "") + ("Buzz" if x%5==0 else "") or x for x in range(1, 20) ]
for i in fb:
print(i)
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x = 5
("Fizz" if x%3==0 else "")
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x = 15
("Fizz" if x%3==0 else "") + ("Buzz" if x%5==0 else "")
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Note: or and and return the value of the last expression they evaluate:
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a = "hi"
b = "hello"
a or b
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x = 10
x or 2/0
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x = 15
("Fizz" if x%3==0 else "") + ("Buzz" if x%5==0 else "") or x
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3.11 Dictionaries
- Collections of values indexed by keys:
my_dictionary = {key1:value1, key2:value2, ...}
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game_scores = {}
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game_scores["John"] = 100
game_scores["Ann"] = 120
game_scores["Tom"] = 70
game_scores
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Values can be retrieved and modified by key:
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game_scores["Ann"]
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game_scores["Ann"] = 130
game_scores
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Adding new records:
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game_scores["Beth"] = 0
game_scores
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Iteration on keys:
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for name in game_scores:
print(name, game_scores[name])
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def add(x, y):
z = x+y
return z
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add(2, 3)
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add("hello ", "world!")
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from time import sleep
def timer(seconds, message = "Time's up!"):
for t in range(seconds,0,-1):
print(t)
sleep(1)
print(message)
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timer(10)
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timer(5, message = "Boom!")
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class Player:
name = None
score = 0
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class Player:
name = None
score = 0
def bonus(self, percent):
self.score = int(self.score * (1 + percent/100))
def __str__(self):
return f"Name: {self.name}\nScore: {self.score}"
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p = Player()
p.name = "John"
p.score = 10
print(p)
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p.bonus(50)
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print(p)
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q = Player()
print(q)
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q.name = "Beth"
q.score = 20
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print(q)
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dir(q)
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Note: In Python everything is an object.
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[1, 2, 3].__class__
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dir([1, 2, 3])
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[1, 2, 3].__add__([4,5])
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