Beginning Programming in Python
Fall 2019
Agenda
- Functions
- Function definitions and function calls
- Docstrings
- Return values
- None and the default return value
- The stack: getting to grips with functions and control flow
- A few common mistakes about functions
Functions
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Functions perform some task - mini program
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May take arguments/parameters
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My return a value that can be used late
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- Functions are a convenient way of organizing and structuring the code.
Function Definition
Calling a function
Function Example
docstring Example
return value Example
Yet another Example
Use of return for control flow
return in all flows
return as a substitute for break
5 minutes break!
None
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None is a "null" value.
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If you don't return something, the function returns None
x = print("hello")
print(x)
def helloWorld():
print("Hello, world!")
return None
x = helloWorld()
print(x)Function stack
Few mistakes
# Return and print are not the same:
def sum(x, y):
return print(x + y)
z = sum(5, 10)
print("The return value is:", z)# Global variables are not function arguments
kilos = 11
def kilos_to_pounds(kilos):
return kilos * 2.205
kilos_to_pounds(10)putting it all together
Lecture challenge
Questions?
CSE 20 - Lecture 6
By Narges Norouzi
