is is used to check if two variables are the same object. Often used to check if a variable is None.
import math
print('# is #')# is #
# immutable
a = 100
b = 100
print(a is b) # True
# mutable
a = [100, 200, 300]
b = [100, 200, 300]
print(a is b) # False # a is not b
print(a == b) # True # but a is equal to b
# is not #
a = 100
b = a
print(a is not b) # False
and can be used to make sure a variable has a valid value before performing a operation. Valid value meaning not 0, an empty list, or None.
print('# and #')# and #
a = True
b = False
print(a and b) # False
a = 10
b = 5
print(a and b) # 5
# and operator returns a if it is false otherwise it returns b
# and short circuits
True and print("short circuit") # short circuit
False and print("short circuit") #
try:
a = 10
b = 0
c = a/b
except Exception as e:
print(e) # division by zero
a = 10
b = 0
c = b and a/b # since b is 0 (which is false) the and operator short circuits and returns 0
print(c) # 0
or can be used as a back up value if the first value is False (0, empty list, or None).
print('# or #')# or #
a = True
b = False
print(a or b) # True
lang = None or 'Python'
print(lang) # Python
lang = 'Java' or 'Python'
print(lang) # Java
print('# floor and modulo #')# floor and modulo #
# floor
print(101/4) # 25.25
print(101//4) # 25
print(10/3) # 3.333
print(10//3) # 3
print(math.floor(3.3)) # floor rounds down so 3.3 becomes 3 # 3
print(-10/3) # -3.33
print(-10//3) # -4
print(math.floor(-3.3)) # floor rounds down so -3.3 becomes -4 # -4
Modulo is used to get the reminder of a division operation.
# modulo
print(10 % 4) # 2
print(2451 % 1) # 0
print(2451 % 10) # 1
print(2451 % 100) # 51
seconds = 100000
print("Days: "+str(int(seconds/60/60/24))) # 1
print("Hours: "+str(int(seconds/60/60)%24)) # 3
print("Minutes: "+str(int(seconds/60)%60)) # 46
print("Seconds: "+str(seconds%60)) # 40
# tilde
print(~5) # -6
# it is the same as -x -1
numbers = [1,2,3,4,5]
for i in range(len(numbers)):
temp = numbers[i]
numbers[i] = numbers[~i]
numbers[~i] = temp