Python Cheat Sheet - Keywords

Keyword	Description	Code example
False, True	Data values from the data type Boolean	False == (1 > 2), True == (2 > 1)
and, or, not	Logical operators: (x and y) -> both x and y must be True (x and y) -> both x and y must be True (x or y) -> either x or y must be True (not x) -> x must be false	x, y = True, False (x or y) == True # True (x and y) == False # True (not y) == True # True
break	Ends loop prematurely	while(True): break # no infinite loop print("hello world")
continue	Finishes current loop iteration	while(True): continue print("43") # dead code
class	Defines a new class + a real-world concept (object oriented programming)	class Beer: def __init__(self): self.content = 1.0 def drink(self): self.content = 0.0 becks = Beer() # constructor - create class becks.drink() # beer empty: b.content == 0</br
def	Defines a new function or class method. For latter, first parameter ("self") points to the class object When calling class method, first parameter is implicit.	def incrementor(x): return x + 1 incrementor(4) # returns 5
if, elif, else	Conditional program execution: program starts with "if" branch, tries the "elif" branches, and finishes with "else" branch (until one branch evaluates to True).	x = int(input("your value: ")) if x > 3: print("Big") elif x == 3: print("Medium") else: print("Small")
for, while	# For loop declaration for i in [0,1,2]: print(i)	# While loop - same semantics j = 0 while j < 3: print(j) j = j + 1
in	Checks whether element is in sequence	42 in [2, 39, 42] # True
is	Checks whether both elements point to the same object	y = x = 3 x is y # True [3] is [3] # False
None	Empty value constant	def f(): x = 2 f() is None # True
lambda	Function with no name (anonymous function)	(lambda x: x + 3)(3) # returns 6
return	Terminates execution of the function and passes the flow of execution to the caller. An optional value after the return keyword specifies the function result.	def incrementor(x): return x + 1 incrementor(4) # returns 5

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