1. Week 2 Lab2 Practice Dina A. Said dasaid@ucalgary.ca

2. Functions: Parameter Passing  To pass a parameter to a function, define it as a variable in the function declaration e.g. def square(length)  At run time, call the function with the value of this parameter e.g. square(6)  Example:  def printNameID(name,ID): print name print ID  At the command window write: printNameID(“John”,122898) 3/18/2009CPSC203- Week2- Lab2

3. Functions: return value  Your function may return a value using return command, e.g. return 6 return sum  Note that, you should return only one value  If a function returns a value, you can use it in assignment  e.g. F=mySum() Now, you have defined a variable F that will holds the value that the function mySum() returns 3/18/2009CPSC203- Week2- Lab2

4. Example 3/18/2009CPSC203- Week2- Lab2 def mySum(): sum=0 for x in (1,2,3): sum=sum+x return sum In command window: mySum() F=mySum() Print F

5. Exercise  Modify the previous function to return the summation of numbers in a range starting from x to y, where x and y are parameters passed to your function  Test your function with mySum(1,3)  You answer should be 6  Note:  If the range is required to be inclusive, your range should be (x,y+1)  However, if the range is required to be exclusive, your range should be (x+1,y)  The default is inclusive 3/18/2009CPSC203- Week2- Lab2

6. 3/18/2009CPSC203- Week2- Lab2 def mySum(x,y): sum=0 for no in range (x,y+1): sum=sum+no return sum Note that you can’t have two variables with the same name

7. Example  Write a function returns the multiplication of numbers in range starting from x to y.  Test your function with  myMul(2,3)  2*3=6  myMul(2,6)  2*3*4*5*6=720 3/18/2009CPSC203- Week2- Lab2

8. 3/18/2009CPSC203- Week2- Lab2 def myMul(x,y): mul=1 for n in range (x,y+1): mul=mul*n return mul Initialization

9. Exercise  Write a function that returns the Permutations of a given number, where the permutation of x is calculated as 1*2*…*x. For example, the permutation of 6 is calculated as 1*2*3*4*5*6=720 and the permutation of 7 is calculated as 1*2*3*4*5*6*7=5040  Hints:  Think about the range of your loop from 1 to the number  Use multiplication  What value should you initialize the permutation with? 3/18/2009CPSC203- Week2- Lab2

10. Exercise  Modify the permutation program to check first if the given number if greater than zero. You should print error message otherwise.  What is the return value in case of error message? 3/18/2009CPSC203- Week2- Lab2

11. 3/18/2009CPSC203- Week2- Lab2 def perm(x): if (x<=0): print "Error" return -1 else: result=1 for n in range (1,x+1): result=result*n return result

12. Example  Write a function that accepts four numbers and returns the maximum of them 3/18/2009CPSC203- Week2- Lab2 def myMax(x,y,z,w): max=x for n in (y, z, w): if (n>max): max=n return max max=x=3 n=y=6 is n>max? yes  max =6 n=z=2 is n>max? No  do nothing n=w=9 is n>max? yes  max =9 myMax(3,6,2,9) X=3 y=6 z=2 w=9

13. Exercise  Write a function that accepts 3 numbers and returns the minimum of them  Test your program with  myMin(9,5,2)  2  myMin(3,4,10)  3  myMin(2,-4,8)  -4 3/18/2009CPSC203- Week2- Lab2