# Chapter 6: Loops¶

## Example square.c, Page 102¶

In [3]:
def main():
print "This program prints a table of squares."
n=int(raw_input("Enter number of entries in table: ")) #input number of entries
i=1 #variable declaration
while(i<=n):
print "%10d%10d" % (i,i * i) #printing number and it's square
i=i+1
if  __name__=='__main__':
main()

This program prints a table of squares.
Enter number of entries in table: 5
1         1
2         4
3         9
4        16
5        25


## Example sum.c, Page 103¶

In [6]:
def main():
sum=0
print "This program sums a series of integers."
n=int(raw_input("Enter integers (0 to terminate): ")) #input the integers to operate on
while(n!=0):
sum=sum+n #calculating sum till 0 encountered
n=input()
print "The sum is: %d" % sum #printing sum
if  __name__=='__main__':
main()

This program sums a series of integers.
Enter integers (0 to terminate): 8
23
71
5
0
The sum is: 107


## Example numdigits.c, Page 105¶

In [7]:
def main():
digits=0 #initialise
n=int(raw_input("Enter a nonnegative integer: ")) #input the number
n=n/10
digits=digits+1
#finding number of digits
while(n>0):
n=n/10
digits=digits+1
print "The number has %d digit(s)." % digits #printing answer

if  __name__=='__main__':
main()

Enter a nonnegative integer: 60
The number has 2 digit(s).


## Example square2.c, Page 110¶

In [12]:
def main():
print "This program prints a table of squares."
n=int(raw_input("Enter number of entries in table: ")) #input number of entries
for i in range (1,(n+1)):
print "%10d%10d" % (i,i * i) #printing number and it's square

if  __name__=='__main__':
main()

This program prints a table of squares.
Enter number of entries in table: 5
1         1
2         4
3         9
4        16
5        25


## Example square3.c,Page 110¶

In [14]:
def main():
print "This program prints a table of squares."
n=int(raw_input("Enter number of entries in table: ")) #input number of entries

#variable declaration
i=1
odd=3
square=1
#calculation
for i in range (1,(n+1)):
print "%10d%10d" % (i,square)
square=square+odd
odd=odd+2

if  __name__=='__main__':
main()

This program prints a table of squares.
Enter number of entries in table: 5
1         1
2         4
3         9
4        16
5        25


## Example checking.c, Page 115¶

In [17]:
def main():
balance=0.0 #initialise
print "*** ACME checkbook-balancing program ***"
print "Commands: 0=clear, 1=credits, 2=debit, 3=balance, 4=exit"
print ""
while(1):
cmd=int(raw_input("Enter command: "))

#operate on balance according to the option selected
if cmd==0:
balance=0.0 #clear balance
elif cmd==1:
credit=float(raw_input("Enter amount of credit: "))
balance=balance+credit #credit
elif cmd==2:
debit=float(raw_input("Enter amount of debit: "))
balance=balance-debit #debit
elif cmd==3:
print "Current balance: $%0.2f" % balance #show current balance elif cmd==4: return 0 #exit else: print "Commands: 0=clear, 1=credits, 2=debit, 3=balance, 4=exit" if __name__=='__main__': main()  *** ACME checkbook-balancing program *** Commands: 0=clear, 1=credits, 2=debit, 3=balance, 4=exit Enter command: 1 Enter amount of credit: 1042.56 Enter command: 2 Enter amount of debit: 133.79 Enter command: 1 Enter amount of credit: 1754.32 Enter command: 2 Enter amount of debit: 1400 Enter command: 2 Enter amount of debit: 68 Enter command: 2 Enter amount of debit: 50 Enter command: 3 Current balance:$1145.09
Enter command: 4

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