# Chapter 4 : Conditionals and recursion¶

### example 4.1 page no :34¶

In [1]:
'''
example 4.1 page no :34
'''

def printParity (x):
if (x%2 == 0):
print "x is even"
else:
print "x is odd"

printParity (17)

x is odd


### example 4.2 page no :36¶

In [2]:
'''
example 4.2 page no :36
'''
import math

def printLogarithm (x):
if (x <= 0.0):
return;
result = math.log(x);
print "The log of x is " , result;

printLogarithm(-1)
printLogarithm(5)

Positive numbers only, please.
The log of x is  1.60943791243


### example 4.3 page no : 37¶

In [3]:
'''
example 4.3 page no : 37
'''

def countdown (n):
if (n == 0):
print  "Blastoff!"
else:
print n
countdown (n-1)

countdown(5)

5
4
3
2
1
Blastoff!


### example 4.4¶

In [4]:
'''
example  4.4
'''
import math
def printLogarithm(x):
if (x <= 0.0):
print "Positive numbers only, please." << endl;
return;
result = math.log(x)
print "The log of x is " , result;

def countdown (n) :
if (n == 0):
print "Blastoff!"
else:
print n
countdown (n-1);

countdown (3);
printLogarithm(10)

3
2
1
Blastoff!
The log of x is  2.30258509299

In [ ]: