- if statement
def f(x):
print("A", end="")
if (x == 0):
print("B", end="")
print("C", end="")
print("D")
f(0)
f(1)
A more interesting example:
# These examples define abs(n), which is a nice example here, but it is
# also a builtin function, so you do not need to define it to use it.
def abs1(n):
if (n < 0):
n = -n
return n
# again, with same-line indenting
def abs2(n):
if (n < 0): n = -n # only indent this way for very short lines (if at all)
return n
# again, with multiple return statements
def abs3(n):
if (n < 0):
return -n
return n
# aside: you can do this with boolean arithmetic, but don't!
def abs4(n):
return (n < 0)*(-n) + (n>=0)*(n) # this is awful!
# now show that they all work properly:
print("abs1(5) =", abs1(5), "and abs1(-5) =", abs1(-5))
print("abs2(5) =", abs2(5), "and abs2(-5) =", abs2(-5))
print("abs3(5) =", abs3(5), "and abs3(-5) =", abs3(-5))
print("abs4(5) =", abs4(5), "and abs4(-5) =", abs4(-5))
- if-else statement
def f(x):
print("A", end="")
if (x == 0):
print("B", end="")
print("C", end="")
else:
print("D", end="")
if (x == 1):
print("E", end="")
else:
print("F", end="")
print("G")
f(0)
f(1)
f(2)
Revisiting abs(n):
def abs5(n):
if (n >= 0):
return n
else:
return -n
# or, if you prefer...
def abs6(n):
if (n >= 0):
sign = +1
else:
sign = -1
return sign * n
print("abs5(5) =", abs5(5), "and abs5(-5) =", abs5(-5))
print("abs6(5) =", abs6(5), "and abs6(-5) =", abs6(-5))
- if-else expression
# if-else expression (not an if-else statement!)
def abs7(n):
return n if (n >= 0) else -n
print("abs7(5) =", abs7(5), "and abs7(-5) =", abs7(-5))
- if-elif-else statement
def f(x):
print("A", end="")
if (x == 0):
print("B", end="")
print("C", end="")
elif (x == 1):
print("D", end="")
else:
print("E", end="")
if (x == 2):
print("F", end="")
else:
print("G", end="")
print("H")
f(0)
f(1)
f(2)
f(3)
A more interesting example:
def numberOfRoots(a, b, c):
# Returns number of roots (zeros) of y = a*x**2 + b*x + c
d = b**2 - 4*a*c
if (d > 0):
return 2
elif (d == 0):
return 1
else:
return 0
print("y = 4*x**2 + 5*x + 1 has", numberOfRoots(4,5,1), "root(s).")
print("y = 4*x**2 + 4*x + 1 has", numberOfRoots(4,4,1), "root(s).")
print("y = 4*x**2 + 3*x + 1 has", numberOfRoots(4,3,1), "root(s).")
Another example:
def getGrade(score):
if (score >= 90):
grade = "A"
elif (score >= 80):
grade = "B"
elif (score >= 70):
grade = "C"
elif (score >= 60):
grade = "D"
else:
grade = "F"
return grade
print("103 -->", getGrade(103))
print(" 88 -->", getGrade(88))
print(" 70 -->", getGrade(70))
print(" 61 -->", getGrade(61))
print(" 22 -->", getGrade(22))
- Incorrect usage
See here.