Tuple

There are three basic sequence types: lists, tuples, and range objects. We've learned about list and range function in previous lessons, let's talk about tuple.

A tuple is a sequence of elements that cannot be modified. It can contain any Python or more values. the items of a tuple are enclosed in parenthesis and separated by commas.

Some tuples: myTuple = ( 1,2,3 ) t2 = ('H', 'e', 'L') t3 = ('College drive', ['A10','B20','C10'], 98008, 'WA', )

tuple packing

t = 3, 6, 9       # Supprise? No error message
print(t)          # (3, 6, 9)
tp = 5, 8, 'Hi'  
print(tp)         # (5, 8, 'Hi')

The above statements like tp = 5, 8, 'Hi' is an example of tuple packing: the values 5,8,'Hi' are packed together in a tuple. You see, the output tuples are always enclosed in parentheses.

Sequence unpacking The reverse operation, sequence unpacking is also possible:

t = 3,6,9
x, y, z = t
print(x,y,z)    # 3,6,9

Remember in lesson (Variables and Values) we mentioned about variables' multiple assignments m, n, l = 2,4,6
Note that multiple assignment is really just a combination of tuple packing and sequence unpacking.

x,y,z = 3,6,9 is the same as x,y,z = (3,6,9), (x,y,z) = (3,6,9) and (x,y,z) = 3,6,9

The construction of tuples containing 0 or 1 items:

empty_tuple = ( )
singleton = 'hello',    # <-- note trailing comma
print(singleton)        # ( 'hello', )   a tuple
print( len(empty_tuple) )       # returns the length of tuple, empty tuple length is 0

tur = (2,4,6,)     # some programmers prefer to include the trailing comma for all tuples

Compare tuple and list, Different: tuple is immutable while list is mutable; Same:

• Just like a list, the elements of a tuple have a defined order. Elements of a tuple is t[0], t[1]...and so on.

• Negative indices count from the end of the tuple.

• [start:stop:step], slicing works too. Slicing doesn't change the original tuple, it just create a new tuple.

• tuple.index(item) returns the index number of an item in a tuple

• max(tuple), min(tuple) returns the max or min value in a tuple,

>>> t = (1,2,3,4,5,6,7,8)
>>> t[2]
3
>>> t[-2]
7
>>> t[3:6]
(4,5,6)
>>> t[-2:-6:-1]
(7,6,5,4) 
>>> t.index( 5 )     # 4, the index of 5 in t
>>> max(t)      # 8, max value in t

Use tuple in CodeCraft

Use a tuple to represent a point in CodeCraft 3D world, (x,y,z)

It's convinent to use tuple of three numbers to indicate a point in 3D coordinates,

p1 = (3, 5, -10)
p2 = (1, 10, -15)
p3 = (-4, 3, -12)

# build blocks using these tuples
block( p1[0], p1[1], p1[2], 'brick')
block( p2[0], p2[1], p2[2], 'obsidian')
block( p3[0], p3[1], p3[2], 'cobblestone')

Loop through a tuple

Similar to list, we can use for loop to iterate through a tuple:

t = (1,4,7,3,9,2)
for item in t:
    print(item)     # 1,4,7,3,9

# see in the CodeCraft world, build some columns

for item in t:
    column( t.index(item) , -20, item, 'brick')  

# highlight the max value in tuple
max = max(t)    
column( t.index(max), -20, max, 'obsidian')

List of tuples

In CodeCraft World, since tuples(x,y,z) can represent locations, a list of tuples would represent various locations. lst = [ t1, t2, t3 ] t1 = (x1, y1, z1) t2 = (x2, y2, z2) t3 = (x3, y3, z3)

lst[listIndex][tupleIndex]

The list represents three points t1, t2, t3, and point t1 has coordinates: (x1,y1,z1)...

lst[1][2] indicates: t2, z2 ( z value of the second point)

>>> P= [(1,1,-5), (4,5,-7), (8,3,-10)]
>>> P[1][2]     # -7 (z of the second point)

>>> P[0][1]     # 1 (y of the first point)

===

(extra? in Ch.5, complex structures)

(use list of tuples, ) List of tuples representing some selected location coordinates (x,y,z)

4-01-2 Some blocks in the air

# 4-01-2
# us a tuple list to store the locations (x,y,z)
lst = [(2,8,-10),(5,15,-15),(12,3,-20),(16,10, -10)]

# put a bar_z at the first tuple indicated location (2,8,-10)
bar_z(lst[0][0], lst[0][1], lst[0][2], 5, 'dirt')

for i in lst:
    block(i[0],i[1],i[2],10,'quartz')

We can use list of tuples to store some location coordinates (x,y,z), then build some structures at these selected locations, the above app just put some blocks.