library(reticulate  )

## Warning: package 'reticulate' was built under R version 3.4.4

Reading Material

For this material we will be following Chapter 10 of the Python for Everybody text by Charles Severance. A pdf of the text is posted in Moodle.

Tuples

A tuple is a sequence of values separated by commas. A tuple may or may not be enclosed in parentheses.

Here are some examples.

t1 = 1,2,3
t2 = (1,2,3)
print(t1)

## (1, 2, 3)

print(t2)

## (1, 2, 3)

Note that in both cases print() enclosed the tuples in parentheses.

Doodle Create your own simple exercise to demonstrate the contents of this slide.

Extracting by Index

Values of tuple components may be extracted by numerical index in the same way as lists or strings. Slicing also works in exactly the same way.

Examples

x = t1[0]
print(x)

## 1

z = t1[-1]
print(z)

## 3

Doodle Create your own simple exercise to demonstrate the contents of this slide.

Combining Tuples

The same concatenation and repetitin we used with strings works with tuples.

Examples

t3 = ('a','b','c')
print(t1+t3)

## (1, 2, 3, 'a', 'b', 'c')

print(2*t1+t3)

## (1, 2, 3, 1, 2, 3, 'a', 'b', 'c')

print(2*(t1+t3))

## (1, 2, 3, 'a', 'b', 'c', 1, 2, 3, 'a', 'b', 'c')

Doodle Create your own simple exercise to demonstrate the contents of this slide.

Tuples are Immutable

Example

The following line of code will fail. Try it in idle or cocalc.

# t1[0] = 4
print(t1[0])

## 1

Doodle Create your own simple exercise to demonstrate the contents of this slide.

Note on Immutability

A tuple may contain items of any type. If an item in a tuple is mutable. The mutable item may be changed and this will be reflected in the tuple.

Example

List1 = [1,2,3]
List2 = [4,5,6]
tt = (List1,List2)
print(tt)

## ([1, 2, 3], [4, 5, 6])

List1.append('a')
print(tt)

## ([1, 2, 3, 'a'], [4, 5, 6])

Doodle Create your own simple exercise to demonstrate the contents of this slide.

Conversion

A tuple may be converted to another data structure containing the same data. Lists have many methods that can alter them and sets are useful for unduplication

Example

L1 = list(t1)
print(L1)

## [1, 2, 3]

S1 = set(t1)
print(S1)

## {1, 2, 3}

Doodle Create your own simple exercise to demonstrate the contents of this slide.

Multiple Assignment

Multiple assignment is a valuable coding technique which allows us to extract the values in a tuple and assign them to specific variables. There must be exacly the same number of variables as values in the tuple.

Example

print(t1)

## (1, 2, 3)

First, Second, Third = t1
print(First)

## 1

print(Second)

## 2

print(Third)

## 3

Doodle Create your own simple exercise to demonstrate the contents of this slide.

Multiple Assignment (Complex)

def findExtremeDivisors(n1, n2):
    minVal, maxVal = None, None
    for i in range(2, min(n1, n2) + 1): 
        if n1%i == 0 and n2%i == 0: 
            if minVal == None or i < minVal: 
                minVal = i 
            if maxVal == None or i > maxVal: 
                maxVal = i 
    
    return (minVal, maxVal)
lcd, gcd = findExtremeDivisors(27,18)
print(lcd)

## 3

print(gcd)

## 9

Comparison

Tuples may be compared. Equality requires that both tuples have the same values in the same places. Comparison starts on the left and continues until a tie-breaker is found.

Examples

ta = (1,3,2)
tb = (1,2,3)
print(ta == tb)

## False

print(ta < tb)

## False

print(ta > tb)

## True

Doodle Create your own simple exercise to demonstrate the contents of this slide.