• We create a new function using the def keyword follow by optional parameters in parentheses
• We indent the body of the function

def print_lyrics():
	print("hear is a little song i wrote")
	print('please listen carefullly note to note')
	print('don''t worry be happy')

The code inside the def is not calling ,it’s remembering it’s figuring out and it will ready when we call it

x = 5
#if int(x) == 5:
print('hello')
def print_lyrics():
   print("hear is a little song i wrote")
   print('please listen carefullly note to note')
   print('don''t worry be happy')
print('yo')
#print_lyrics()
x = x+4
print(x)

Output

hello
yo
9

in this case it will not print out the function print_lyrics be cuz we just define it but doesn’t mean we invoke it or call it

x = 5
print('hello')
def print_lyrics():
   print("hear is a little song i wrote")
   print('please listen carefullly note to note')
   print('don''t worry be happy')
print('yo')
print_lyrics()
x = x+4
print(x)

Output

hello
yo
hear is a little song i wrote
please listen carefullly note to note
dont worry be happy
9

we invoke it using its name

• Once we defined a function we can all or invoke it as many time as we like
• this is the store and reuse pattern

>>> def great(lang):
	if lang == 'es':
		print('hola')
	elif lang == 'fr':
		print('hello')

		
>>> great('es')
hola
>>> great('fr')
hello

this is written on shell

this code like a translator

Return Values

Questions:

• What will the following Python program print out?:

    def fred():
        print("Zap")
    def jane():
        print("ABC")
      
    jane()
    fred()
    jane()
  

• Ans

    ABC
    Zap
    ABC
  

  ---

  # Real Exercise

  • 1 make function using def

      def computepay(hours,rate):
          print ('in computepay')
      sh = input('Enter Hours: ')
      sr = input ('Enter Rate:')
      fh = float (sh)
      fr = float(sr)
            
      if fh  > 40:
          reg = fr*fh
          otp = (fh - 40.0) *(fr * 0.5)
          xp = reg +otp
      else:
          xp = fh * fr
      print ('pay:',xp)
    

    ### Output

      Enter Hours: 40
      Enter Rate:10
      pay: 400.0
    

    in this case it doesn’t run the function computepay because we just define the function but we didn’t invoke it so it doesn’t show up

      def computepay(hours,rate):
          print ('in computepay')
      sh = input('Enter Hours: ')
      sr = input ('Enter Rate:')
      fh = float (sh)
      fr = float(sr)
      computepay(fh,fr)
      if fh  > 40:
          reg = fr*fh
          otp = (fh - 40.0) *(fr * 0.5)
          xp = reg +otp
      else:
          xp = fh * fr
      print ('pay:',xp)
    

    ### Output

      Enter Hours: 40
      Enter Rate:10
      in computepay
      pay: 400.0
    

    it shown up when we invoke it

  • 2 put something more into a function

      def computepay(hours,rate):
          print ('in computepay', hours,rate)
          if fh  > 40:
              reg = hours*rate
              otp = (hours - 40.0) *(rate * 0.5)
              pay = reg +otp
          else:
              pay = hours * rate
          print('Returning',pay)
          return pay
      sh = input('Enter Hours: ')
      sr = input ('Enter Rate:')
      fh = float (sh)
      fr = float(sr)
      xp = computepay(fh,fr)
            
      print ('pay:',xp)
    

    Now we put the function , we move the if and else to def then we change something in that function but it still work the same just put some step of calculating into the function

    ### Output

      Enter Hours: 40
      Enter Rate:10
      in computepay 40.0 10.0
      Returning 400.0
      pay: 400.0