Class 7a: Functions

The plan!
Basics: data types (and operations & calculations)
Basics: conditionals & iteration
Basics: lists, tuples, dictionaries
Basics: writing functions
Reading & writing files: opening, parsing & formats
Working with numbers: numpy & scipy
Making plots: matplotlib & pylab
… if you guys want more after all of that …
Writing better code: functions, pep8, classes
Working with numbers: Numpy & Scipy (advanced)
Other modules: Pandas & Scikit-learn
Interactive notebooks: ipython & jupyter
Advanced topics: virtual environments & version control

functions
# lets define a function
def print_hello(name):
print "Hello", name, ", it's a nice day for functions!"
# now we can call (or run, or execute) the function
print_hello("Marc")

functions
print_hello("Marc") Defining the function:
def function_name(arg1, arg2, ...):
do stuff here
Running the function:
function_name(value1, value2, ...):
indentation!

functions
print_hello("Marc")
# let's add some arguments
def print_hello(name, weather):
print "Hello", name, ", it's", weather.
print "Perfect weather for writing functions!"
print_hello("Marc", "Sunny")
print hello("Gengis", "Raining")
# arguments are optional
def print_hello():
print "Hello, this function is a little boring, right?"
# to run a function with 0 arguments, use empty parentheses
print_hello()
Defining the function:
do stuff here
function_name(value1, value2, ...):
indentation!

functions
# the function definition can be any code!
def print_hello(name, weather, number):
print "Hello", name, ", it's", weather.
if weather == "Sunny":
print "Go outside and play!"
else:
print "Stay inside and program!"
print "Here are some numbers:"
for i in range(number):
print i
print "This is one hell of a long function!"
# nothing happens until the function is run!
print_hello("Marc","Raining", 200)

exercise! wohoo!
Write function that takes two arguments: a name and a number. The function then
prints the name "number" time.
---- names.py ----
def name_repeat(????):
????
????
????
name_repeat("Marc", 10)

functions: arguments
# positional arguments are defined by their position
def print_hello(name, weather,):
print "Hello", name, ", the weather is", weather.
print_hello("Stormy", "Thor")

# keyword arguments are optional, and have default values.
def print_hello(name, weather, drink= "Tea", snack= "Cookie"):
print "Hello", name, ", the weather is", weather
print "Why don’t you drink a ", drink, "with some", snack
print_hello("Marc", "Sunny", drink="Beer", snack="Tremocos")

Defining arguments:
def function_name(arg1, arg2, … kwarg1=default1, kwarg2=default2, … ):
Code goes here
positional keyword

# keyword arguments are optional, and the order doesn’t matter
print_hello("Bob","Rainy")
print_hello("Bob","Rainy", snack="Cake", drink="Coffee")

functions: returning values
# functions are not usually used for printing
# typically they return a value
def times_two_plus_three(x):
return x * 2 + 3
# we can now use this function
n = times_two_plus_three(5)
print n

return x * 2 + 3
print n
do stuff here
return some_value
answer = function_name(value1, value2, ...):

return x * 2 + 3
print n
# let's make it a little more complicated.
# and add some documentation as well
def my_complex_calculation(a, b, c):
""" This returns the value of:
a * b + c
"""
result = x * b + c
return result
print my_complex_function(8, 1, 12)
""" Documentation (comment)
"""
do stuff here
return some_value
answer = function_name(value1, value2, ...):

exercises!
- Write function that takes three inputs (numbers x, y and z), and produces the
result of : a + b - c. Use return to be able to store and use the value later.
---- calc.py ----
def my_calculation(????):
????
????
????
x = my_calculation(12, 13, 14)
print "The complex calculation with 12, 13 and 14 resulted in", x
version 2: as above, but if no numbers for b or c are specified, use 5 and 10 as default
values.

Class 7a: Functions

More Related Content

What's hot (19)

Viewers also liked (10)

Similar to Class 7a: Functions (20)

Recently uploaded (20)

Class 7a: Functions