Functions & Built in Functions

Question 1

Higher Order Functions

Answer 1

A function that either:

• takes one or more functions as arguments
• returns a function as a result

def higher_ord ( f, *args ) :

result = f ( *args )

return result

Question 2

methods

(def, how to call, function to find information)

Answer 2

• a function that is avaiable to a given object because of the object type; a function that belongs to an object
• .method_name( )
• help( object.method)

Question 3

lambda function example and standard function equivilent

lambda used with higher oder functions

(3 answers)

Answer 3

( 1 )

add_one = lambda x: x +1

( 2 )

def add_one( x ):

return x + 1

add_one( 2 ) returns 3 in both

( 3 )

high_ord = lambda x, func: x + func( x )

high_ord(2, lambda x: x * x)

Question 4

lambda as an anonymous function

Answer 4

lambda x, y: x + y

_(1, 2) returns 3

the single underscore (_) is bound to the last expression evaluated by the interpretor

Question 5

function general syntax

(how to set a default value)

(setting variable types & dynamic type)

Answer 5

( 1 )

def name_of_function( num1, num2 ):

”””

Docstring explaining the function

”””

do something

return ( num1 + num2 )

( 2 )

def name_of_function( var = ‘some text’) :

= ‘some text’ in the function inputs is the default value

( 3 )

python is a dynamically typed prog. lang., so you cannot define input types in function call

work around: define var types in function body

def add(x, y):

x = int(x)

y = int(y)

return x + y

even when text inputed in function call, will convert to interger values

Question 6

Working with Files in Python

• write a text file in python line of code
• open the text file
• print working directory
• read the file
• .readlines( )
• with open syntax

Answer 6

• %%writefile myfile.txt
• myfile = open(myfile.txt)
• pwd
• .read( )
• returns a list with each line as an element
• with open(filename, mode) as var_name:
  
  • do something
  • ex: contents = var_name.read( )

Question 7

while loop generic example

Answer 7

while some_boolean_condition:

do something

else:

do something different

Question 8

useful functions:

range( ), enumerate( ), zip( ), min( )/max( ), input( )

Answer 8

( 1 )

• range( ) returns a sequence of numbers

for num in range (0, 11, 2):

print(num)

returns even numbers

( 2 )

• enumerate( )

word = ‘abcde’

for item in enumerate(word):

print(item)

return tuple of index and value ex. (0, ‘a’)

can also unpack using tuple unpacking

( 3 )

mylist1 = [1,2,3]

mylist2 = [‘a’,’b’,’c’]

from item in zip(mylist1, mylist2):

print(item)

returns both list items as a tuple

( 1 , ‘ a ‘ ) ( 2 , ‘ b ‘ ) ( 3 , ‘ c ‘ )

( 4 )

min( ) / max( ) # returns the min and max values in a function

( 5 )

ask for user input

accepts anything as a string, must transform/cast it to different data type

Question 9

useful libraries

random

2 functions: shuffle( ) and randint( )

Answer 9

( 1 )

shuffle( ) # randomly shuffles items in a list

mylist = [1, 2, 3, 4]

shuffle(mylist) # returns random order of values

( 2 )

randint( ) # retruns a random integer, similar to a seed

Question 10

return multiple variables in python

Answer 10

use they comma in between return variables in

ex. return even_list, odd_list @ end of func.

Question 11

function annotation

(ex. and def.)

Answer 11

example

def split_comma(line: str) → str :

pass

definition

• this is a variable type hint
• indicating that only string variables can be passed to the function
• this can be used with outher variables types as well

another example

def h_index(citations: List[int]) → int:

pass

• indicates that a list object on integers should be passed to the function