- Some Builtin Types
print("Some basic types in Python:")
print(type(2)) # int
print(type(2.2)) # float
print(type('ABC')) # str (string)
print(type(True)) # bool (boolean)
- Some Builtin Constants
print("Some constants we will use:")
print(True)
print(False)
print(None)
import math
print(math.pi)
- Some Builtin Functions
print("Type conversion functions:")
print(int(2.8)) # convert to an integer (int)
print(float('42')) # convert to a floating point number
print("And some basic math functions:")
print(abs(-5)) # absolute value
print(max(2,3)) # return the max value
print(min(2,3)) # return the min value
print(pow(2,3)) # raise to the given power (pow(x,y) == x**y)
print(round(2.354, 1)) # round with the given number of digits
- Some Builtin Operators
| Category | Operators |
| Arithmetic | +, -, *, /, //, **, % |
| Relational | <, <=, >=, >, ==, != |
| Assignment | +=, -=, *=, /= |
| Logical | and, or, not |
- Types Affect Semantics
print(3 * 2)
print(3 * "abc")
print(3 + 2)
print("abc" + "def")
print(3 + "def")
- Integer Division
print(5/2) # 2.5
print(5//2) # 2
- The Remainder Operator (%)
print(" 6%3 =", ( 6%3))
print(" 5%3 =", ( 5%3))
print(" 1%3 =", ( 1%3))
- Operator Order
print(2+3*4) # prints 14, not 20
-
Approximate Values of Floating-Point Numbers
print(0.1 + 0.1 == 0.2) # True, but...
print(0.1 + 0.1 + 0.1 == 0.3) # False!
print(0.1 + 0.1 + 0.1) # prints 0.30000000000000004 (uh oh)
print((0.1 + 0.1 + 0.1) - 0.3) # prints 5.55111512313e-17 (tiny, but non-zero!)
Equality Testing with almostEqual:
print("The problem....")
d1 = 0.1 + 0.1 + 0.1
d2 = 0.3
print(d1 == d2) # False (never use == with floats!)
print()
print("The solution...")
epsilon = 10**-10
print(abs(d2 - d1) < epsilon) # True!
print()
print("Once again, using a useful helper function, almostEqual:")
def almostEqual(d1, d2):
epsilon = 10**-10
return (abs(d2 - d1) < epsilon)
d1 = 0.1 + 0.1 + 0.1
d2 = 0.3
print(d1 == d2) # still False, of course
print(almostEqual(d1, d2)) # True, and now packaged in a handy reusable function!
- Short-Circuit Evaluation
def yes():
return True
def no():
return False
def crash():
return 1/0 # crashes!
print(no() and crash()) # Works!
print(crash() and no()) # Crashes!
print (yes() and crash()) # Never runs (due to previous crash), but would also crash (without short-circuiting)
Once again, using the "or" operator:
def yes():
return True
def no():
return False
def crash():
return 1/0 # crashes!
print(yes() or crash()) # Works!
print(crash() or yes()) # Crashes!
print(no() or crash()) # Never runs (due to crash), but would also crash (without short-circuiting)