Loops and Functions

Question 1

Write a for loop that prints out the squares of the numbers 1 through 10.

Answer 1

for i in range(1, 11):
print(i ** 2)

Question 2

Write a very basic function that calculates the squarte of a number

Answer 2

def square_number(x):
return x**2

Question 3

Loop through the letters in the word “banana”:

Answer 3

for x in “banana”:
print(x)

Question 4

Exit the loop when x is “banana”:

fruits = [“apple”, “banana”, “cherry”]

Answer 4

fruits = [“apple”, “banana”, “cherry”]
for x in fruits:
print(x)
if x == “banana”:
break

• returns “apple” and “banana”

Question 5

Exit the loop when x is “banana”, but this time the break comes before the print:

fruits = [“apple”, “banana”, “cherry”]

Answer 5

fruits = [“apple”, “banana”, “cherry”]
for x in fruits:
if x == “banana”:
break
print(x)

-returns just “apple”

Question 6

Do not print banana:

fruits = [“apple”, “banana”, “cherry”]

Answer 6

fruits = [“apple”, “banana”, “cherry”]
for x in fruits:
if x == “banana”:
continue
print(x)

Question 7

what does range() do?

Answer 7

The range() function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and ends at a specified number.

Question 8

for x in range(6):
print(x)

Is range(6) the values of 0 to 6 or 0 to 5?

Answer 8

0-5

Question 9

for x in range():
print(x)

convert to make the loop start at 2 and end at 5

Answer 9

for x in range(2, 6):
print(x)

Question 10

for x in range():
print(x)

convert to make loop start at 2, end at 30, but loop in increments of 3

Answer 10

for x in range(2, 30, 3):
print(x)

Question 11

Print all numbers from 0 to 5, and print a message when the loop has ended:

Answer 11

for x in range(6):
print(x)
else:
print(“Finally finished!”)

Question 12

for x in range(6):
if x == 3: break
print(x)
else:
print(“Finally finished!”)

is the else block executed?

Answer 12

If the loop breaks, the else block is not executed.

Question 13

What’s a nested loop?

Answer 13

A nested loop is a loop inside a loop.

The “inner loop” will be executed one time for each iteration of the “outer loop”:

Question 14

Print each adjective for every fruit:

adj = [“red”, “big”, “tasty”]
fruits = [“apple”, “banana”, “cherry”]

Answer 14

for x in adj:
for y in fruits:
print(x, y)

Question 15

Define a function (my_function) that prints the first name from this list + the last name, Refsnes:
Emily, Tobias, Linus

Answer 15

def my_function(fname):
print(fname + “ Refsnes”)

my_function(“Emil”)
my_function(“Tobias”)
my_function(“Linus”)

Question 16

what do you do if you do know how many arguments will be passed into your function, say, 2. What’s an example?

Answer 16

def my_function(fname, lname):
print(fname + “ “ + lname)

my_function(“Emil”, “Refsnes”)

Question 17

what’s an example of not passing the right number of arguments through the function, say trying to pass 1 through a function that expects 2 arguments?

Answer 17

def my_function(fname, lname):
print(fname + “ “ + lname)

my_function(“Emil”)

Question 18

what do you do if you do not know how many arguments will be passed into your function?

Answer 18

Add a * before the parameter name in the function definition.

def my_function(*kids):
print(“The youngest child is “ + kids[2])

my_function(“Emil”, “Tobias”, “Linus”)

Question 19

with the following countries, define a function that prints “I am from” + country

sweden, india, norway, brazil

Answer 19

def my_function(country = “Norway”):
print(“I am from “ + country)

my_function(“Sweden”)
my_function(“India”)
my_function()
my_function(“Brazil”)

Question 20

define a function that multiplies the following numbers by 5

Answer 20

def my_function(x):
return 5 * x

print(my_function(3))
print(my_function(5))
print(my_function(9))

Question 21

How do you specify that a function can have ONLY positional arguments, or ONLY keyword arguments

Answer 21

To specify that a function can have only positional arguments, add , / after the arguments:

Question 23

for i in range(1, 11):
print(i ** 2)

Modify this code so that it prints out the squares of the even integers between 1 and 10

Answer 23

for i in range(1, 11):
if i % 2 == 0:
print(i ** 2)

or

for number in range(11):
print (f’orginal: {number} transformed number”: {number**2}’)

Question 24

get data into Python, write a query and execute it using the sqlalchemy library.

Answer 24

database_name = ‘lahman’ # Fill this in with your lahman database name
connection_string = f”postgresql://postgres:postgres@localhost:5432/{database_name}”
engine = create_engine(connection_string)

Question 25

Write a function named collatz that will take as input a number. If that number is even, your function should divide it by two and return the result. If the number is odd, it should triple the number and add one and then return the result.

Answer 25

def collatz(x):
if x % 2:
return x/2
else:
return x*3+1

print(collatz(6))

Question 26

how is range() helpful?

Answer 26

range can be helpful when writing for loops if you want to iterate through a set of consecutive numbers.

Question 27

if we wanted to sum the first 100 positive integers we could do this using the accumulator pattern.

Answer 27

total_sum = 0
for number in range(1, 101):
total_sum += number

print(f’The total sum is {total_sum}’)

Question 28

Find the sum of the squares of all even integers between 2 and 1000.

Answer 28

total_sum=0
for d in range(2, 1001, 2):
total_sum +=(d**2)

total_sum

Question 29

write a very basic function to calculate the square of a number

Answer 29

def square_number(x):
return x**2

Question 30

Write a function get_teams that will take as input a year and which returns the team stats (from the teams table) for the input year.

Answer 30

def get_teams(year):
return teams.loc[teams[‘yearid’] == year]

–then this returns all from 2009:

_2009 = get_teams(2009)
_2009