Python 101 – Part 1

The code and notes from today’s Programming the Pi Session.

Covers an introduction to data types and some of the things we can do with them.

(Note: you can get a sneak peak at part 2 here)

# Variables

# Assigment Operators

x = 1

print(x)

x += 1

print(x)

# x += 1 is equivalent to x = x + 1
# You can use any of the Arithmetic operators in this way

# Types
# =====

# Integers

x = 5
y = 2000
z = -123

# Floats
r = 0.5
t = 3.14159265359
s = -2.567

'''
--------------------
Arithmetic Operators
--------------------
+ (addition)
- (subtraction)
* (multiplication)
/ (division)
% (modulus aka remainder)
** (exponent aka powers )
// (floor division aka rounded down)
'''

z = x * y

print(z)

# Strings

myString = 'Hello World'

print(myString)

# len() gets the length of the string
print(len(myString))

print(myString[1])

print(myString[0])

# we can use ranges
print(myString[0:5])

# no second number runs to the end of the range
print(myString[5:])

# Lists

numbers = [1, 2, 3, 4, 5]

# we can get the number of items in a list with len()
print(len(numbers))

print(numbers)

#You can pull out a specific list item by index
print(numbers[0])

# We can overide list values by index

numbers[0] = 0

print(numbers)

moreNumbers = [6, 7, 8, 9, 10]

# use + to join two lists
allNumbers = numbers + moreNumbers

print(allNumbers)

allNumbers.sort()

print(allNumbers)

allNumbers.reverse()

print(allNumbers)

writtenNumbers = ['One', 'Two', 'Three', 'Four', 'Five']

print(writtenNumbers)

writtenNumbers.sort()

print(writtenNumbers)

# Dictionaries
# Key Value data type

faveColours = {'Rob': 'Blue', 'Dave': 'Red', 'Jane': 'Orange'}

print(faveColours)

print(faveColours['Rob'])

faveColours['Rob'] = 'Purple'

print(faveColours['Rob'])

# Tuples

tupleNumbers = 1, 2, 3, 4, 5

print(tupleNumbers)

# tupleNumbers[0] = 0 <<< This WILL ERROR

# Tuples are IMMUTABLE
# Once set they cannot be changed!
# BUT they can be converted into lists!

listNumbers = list(tupleNumbers)

listNumbers[0] = 0

# Nesting Lists, Dictionaries

allRoutes = [1, 4, 5, 7, 15]

# we can nest lists (and Tuples) within dictionaries or other lists
busRoutes = {'Town': allRoutes, 'Trinity': 4, 'Airport': 15}

print(busRoutes)

print (busRoutes['Town'])

print (busRoutes['Airport'])

#we can nest dictionaries within ditionaries
usefulInfo = {'Width': '9 miles', 'Length': '5 miles', 'Buses': busRoutes}

print(usefulInfo)

print(usefulInfo['Buses'])

# And we can pull out nested items using multiple keys:
print(usefulInfo['Buses']['Town'])

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