01_Introduction to Colab and Python.py

print("Hello World")

#Functions, Conditionals, and Iteration
def HelloWorldXY(x, y):
  if (x < 10):
    print("Hello World, x was < 10")
  elif (x < 20):
    print("Hello World, x was >= 10 but < 20")
  else:
    print("Hello World, x was >= 20")
  return x + y

for i in range(8, 25, 5):  # i=8, 13, 18, 23 (start, stop, step)
  print("--- Now running with i: {}".format(i))
  r = HelloWorldXY(i,i)
  print("Result from HelloWorld: {}".format(r))
  
print(HelloWorldXY(1,2))

#If you want a loop starting at 0 to 2 (exclusive) you could do any of the following
print("Iterate over the items. `range(2)` is like a list [0,1].")
for i in range(2):
  print(i)

print("Iterate over an actual list.")
for i in [0,1]:
  print(i)

print("While works")
i = 0
while i < 2:
  print(i)
  i += 1
  
print("Python supports standard key words like continue and break")
while True:
  print("Entered while")
  break
  
#Numpy and lists
import numpy as np  # Make numpy available using np.

# Create a numpy array, and append an element
a = np.array(["Hello", "World"])
a = np.append(a, "!")
print("Current array: {}".format(a))
print("Printing each element")
for i in a:
  print(i)

print("\nPrinting each element and their index")
for i,e in enumerate(a):
  print("Index: {}, was: {}".format(i, e))  

print("\nShowing some basic math on arrays")
b = np.array([0,1,4,3,2])
print("Max: {}".format(np.max(b)))
print("Average: {}".format(np.average(b)))
print("Max index: {}".format(np.argmax(b)))

print("\nYou can print the type of anything")
print("Type of b: {}, type of b[0]: {}".format(type(b), type(b[0])))

print("\nUse numpy to create a [3,3] dimension array with random number")
c = np.random.rand(3, 3)
print(c)

print("\nYou can print the dimensions of arrays")
print("Shape of a: {}".format(a.shape))
print("Shape of b: {}".format(b.shape))
print("Shape of c: {}".format(c.shape))
print("...Observe, Python uses both [0,1,2] and (0,1,2) to specify lists")

#Colab Specifics
print("\nDoing $ls on filesystem")
!ls -l
!pwd

print("Install numpy")  # Just for test, numpy is actually preinstalled in all Colab instances
!pip install numpy

#Exercise
!pwd
!cd /
!ls -l
print("Hello")