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LearnRemember   PYTHON





Tuples 

 
# ----------------------------------------------
# TUPLES
# ----------------------------------------------
# A tuple is a comma-separated sequence of values.
# Parentheses are common, but commas define the tuple.
#
# A single value in parantheses is not a tuple.
# For a single element, include the final comma.

t1 = 'a', 'b', 'c'
t2 = ('a', 'b', 'c')

print(type(t1))  # <class 'tuple'>
print(type(t2))  # <class 'tuple'>


# -----------------------------
# SINGLE ELEMENT TUPLES
# -----------------------------
# Parentheses alone don NOT crete a tuple.
# The comma does.

t1 = 'a'
t2 = ('a')

print(type(t1))  # <class 'str'>
print(type(t2))  # <class 'str'>

t3 = ('a',)
print(type(t3))  # <class 'tuple'> 


# -----------------------------
# IMMUTABLE
# -----------------------------

# List are mutalbe
mylist = [1, 2, 3]
mylist[0] = 4
print(mylist)  # [4, 2, 3]

# Tuples are immutable
mytuple = (1, 2, 3)

# mytuple[0] = 4 
# TypeError: 'tuple' object does not support item assignment


# --------------------------------
# REPLACING A TUPLE
# --------------------------------
# You cannot change elements,
# but you cand bind the variable to a new tuple.

t = ('a', 'b', 'c', 'd', 'e')
t = ('A',) + t[2:]

print(t)   # ('A', 'c', 'd', 'e')

Variable Swapping 

 
# ---------------------------------
# VARIABLE SWAPPING
# ---------------------------------
# Tuple unpacking makes swapping simple and save.

c = 3
d = 4

c, d = d, c

assert (c, d)   == (4, 3)


# Traditional approach (more verbose)
a = 1
b = 2

tmp = a

a = b
b = tmp

assert (a, b) == (2, 1)


# ------------------------------------------
# UNPACKING (example)
# -----------------------------------------
# Multiple variables can receive values at once.
# This is extremely common in Python code.

name, domain = "office@google.com".split('@')

assert name == "office"
assert domain == "google.com"

Tuples as Dictionaries Keys 

 
# ---------------------------------------
# TUPLES AS DICTIONARY KEYS
# ---------------------------------------
# Tuples are often uses as compound keys.


phonebook = {
    ("Johny", "Cash"): 4007344455,
    ("John", "Lennon"): 400768696,
}

for first, last in phonebook:
    print(first, last, phonebook[first, last])
    # Johny Cash 4007344455
    # John Lennon 400768696

Tuples and Functions 

 
# --------------------------------------
# MULTIPLE RETURN VALUES
# --------------------------------------
# Functions return ONE object.
# That object is often a tuple.
#
# Example:
#   - Quontient & Reminder:
#
# To compute the quontient and reminders 
# it is better to compute both at the same time.

quot = 7//3
rem = 7%3

assert (quot, rem) == (2, 1)

quot, rem = divmod(7, 3)  # built-in function (returns tuple)

assert (quot, rem) == (2, 1)


# ------------------------------------------
# UNPACKING ARGUMENTS
# ------------------------------------------
# * expands a tuple into separate arguments.
#
# Functions can take a variable number of arguments.
# A parameter name that begins with * gathers arguments into a tuple.

t = (7, 3)
# divmod(t)  
# TypeError: divmod expected 2 arguments, got 1

assert divmod(*t) == (2, 1)  # it works!




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