3.7.0 (v3.7.0:1bf9cc5093, Jun 26 2018, 23:26:24) 
[Clang 6.0 (clang-600.0.57)]
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# Booleans
# Boolean data can only take on one of two values: True and False
True
True
False
False
type(True)
<class 'bool'>
# These two are reserved keywords in Python..no assigning variables with these
# names!
True = "hi"
Traceback (most recent call last):
  Python Shell, prompt 7, line 1
Syntax Error: can't assign to keyword: <string>, line 1, pos 0
type(True), type(False)

# Boolean values are designed to represent the "truth values" of statements
# in Python
# one way to get a truth value: comparison operators 
5 > 4
True
12 < 3
False
a = 12
a < 3
False
13 - a >= 0
True
# interval comparison
3 < 5 < 7
True
2 <= 2 < 3
True
1 < 7 < 3
False
1 < 7 > 3
True
# We can check equality, if two values are 'equal' to each other
a
12
a == 12
True
a == 17 - 1
False
# note the difference between == and =
# == is the equality operator
# = is the assignment operator
# Comparing different types:
7 == 7
True
7 == 7.0
True
'7' == 7.0
False
'7.0' == 7.0
False
'7'== 7
False
'7.0' != 7.0
True
"a" < "b"
True
# Alphabetical order: earlier letters are 'smaller'
"A" < "b"
True
"B" < "a"
True
"#" < "*"
True

# Boolean/logical operators
# Boolean (or logical) operators operate on boolean values, just like arithmetic operators
# operate on numeric values
# arithmetic: 2 + 3, where '+' is the operator
# boolean: True and False, where 'and' is the boolean operator

# 'Boolean' and 'Logical' values are the same thing

# and:
t1 = True
t2 = True
# Given two boolean values, t1, t2, 't1 and t2' gives back  
# True if and only if (iff) t1 and t2 are both True
t1 and t2
True
t2 = False
t1 and t2
False

# or:
# Given two boolean values, t1, t2, 't1 or t2' gives back True iff
# *at least one* of t1 or t2 is True
t1 = True
t2 = True
t1 or t2
True
t2 = False
t1 or t2
True
t1
True
t1 = False
t1 or t2
False

# not 
# Given one boolean value, t, 'not t' returns True iff t is False, and vice versa
t1
False
not t1
True
t2 = True
not t2
False

not True or False
False
not (True or False)
False
# not has a higher precedance than and / or
not False and False
False
(not False) and False
False
not (False and False)
True
not False and False
False

# It is possible to convert other types to bools
bool(0)
False
bool(1)
True
bool(2)
True
bool("hello")
True
bool("")
False
bool(0.0)
False
bool(-1)
True
# For numbers, everything except 0 gets converted to True
# For strings, everything except "" gets converted to True
# These conversions are not used too often in practise, but good to know

# Short-circuiting
False and 4 / 0
False
4 / 0 and False
Traceback (most recent call last):
  Python Shell, prompt 92, line 1
builtins.ZeroDivisionError: division by zero
# 'True and 4/ 0' would also give an error since the and has to check if second
# one is true
bool(4 / 0)
Traceback (most recent call last):
  Python Shell, prompt 93, line 1
builtins.ZeroDivisionError: division by zero
# some more common errors:
a = 3 
b = 6
# How do we check that "a and b are both greater than 5"?
a and b > 5 # do not do this
True
(a > 5) and (b > 5) # use brackets, and separate the comparisons!
False

# Just for fun:
True > False
True
True < False
False