math operations

Question 1

sep=” “

Answer 1

space between two words

Question 2

end=”\n”

Answer 2

end of line

Question 3

int + string
string / integer

Answer 3

unsupported operand type– type error

Question 4

string * 2

Answer 4

stringstring

Question 5

\n

Answer 5

next line

Question 6

"

Answer 6

to escape quotation mark

Question 7

sentense.replace

Answer 7

will replace a word “ I “ or a character

Question 8

f string

Answer 8

string format

Question 9

(x / y)

Answer 9

exact division answer

Question 10

x//y

Answer 10

only whole number

Question 11

x%y

Answer 11

remainder

Question 12

x += 3

Answer 12

x = x + 3

Question 13

x -= 3

Answer 13

x = x - 3

Question 14

x /= 3

Answer 14

x = x / 3

Question 15

x %= 3

Answer 15

x = x % 3

Question 16

x //= 3

Answer 16

x = x // 3

Question 17

x **= 3

Answer 17

x = x ** 3

Question 18

is

Answer 18

Returns True if both variables are the same object

x is y

Question 19

in

Answer 19

Returns True if a sequence with the specified value is present in the object

x in y

Question 20

thislist = [“apple”, “banana”, “cherry”, “orange”, “kiwi”, “melon”, “mango”]
print(thislist[:4])

Answer 20

This example returns the items from the beginning to, but NOT including, “kiwi”:

[‘apple’, ‘banana’, ‘cherry’, ‘orange’]

Question 21

This example returns the items from “cherry” to the end:

thislist = [“apple”, “banana”, “cherry”, “orange”, “kiwi”, “melon”, “mango”]
print(thislist[2:])

Answer 21

This example returns the items from “cherry” to the end:

[‘cherry’, ‘orange’, ‘kiwi’, ‘melon’, ‘mango’]

Question 22

thislist = [“apple”, “banana”, “cherry”, “orange”, “kiwi”, “melon”, “mango”]
print(thislist[-4:-1])

Answer 22

This example returns the items from “orange” (-4) to, but NOT including “mango” (-1):

[‘orange’, ‘kiwi’, ‘melon’]

Question 23

thislist = [“apple”, “banana”, “cherry”]
thislist[1:3] = [“watermelon”]
print(thislist)

Answer 23

Change the second and third value by replacing it with one value:

[‘apple’, ‘watermelon’]

Question 24

thislist = [“apple”, “banana”, “cherry”]
thislist[1:2] = [“blackcurrant”, “watermelon”]
print(thislist)

Answer 24

Change the second value by replacing it with two new values:

​
[‘apple’, ‘blackcurrant’, ‘watermelon’, ‘cherry’]

Question 25

Insert “watermelon” as the third item:

thislist = [“apple”, “banana”, “cherry”]
thislist.insert(2, “watermelon”)
print(thislist)

Answer 25

[‘apple’, ‘banana’, ‘watermelon’, ‘cherry’]

Question 26

To add an item to the end of the list, use the append() method:

Using the append() method to append an item:

thislist = [“apple”, “banana”, “cherry”]
thislist.append(“orange”)
print(thislist)

Answer 26

[‘apple’, ‘banana’, ‘cherry’, ‘orange’]

Question 27

To insert a list item at a specified index, use the insert() method.

The insert() method inserts an item at the specified index:

Example
Insert an item as the second position:

thislist = [“apple”, “banana”, “cherry”]
thislist.insert(1, “orange”)
print(thislist)

Answer 27

[‘apple’, ‘orange’, ‘banana’, ‘cherry’]

Question 28

The remove() method removes the specified item.

Example

Remove “banana”:

thislist = [“apple”, “banana”, “cherry”]
thislist.remove(“banana”)
print(thislist)

Answer 28

[‘apple’, ‘cherry’]

Question 29

Addition + and subtraction - has the same precedence, and therefor we evaluate the expression from left to right:

print(5 + 4 - 7 + 3)

Answer 29

2

Question 30

List Comprehension

List comprehension offers a shorter syntax when you want to create a new list based on the values of an existing list.

Example:

Based on a list of fruits, you want a new list, containing only the fruits with the letter “a” in the name.

Without list comprehension you will have to write a for statement with a conditional test inside:

Example
fruits = [“apple”, “banana”, “cherry”, “kiwi”, “mango”]
newlist = []

for x in fruits:
if “a” in x:
newlist.append(x)

print(newlist)

Answer 30

[‘apple’, ‘banana’, ‘mango’]

Question 31

Condition
The condition is like a filter that only accepts the items that valuate to True.

Example
Only accept items that are not “apple”:

newlist = [x for x in fruits if x != “apple”]

Answer 31

The condition is like a filter that only accepts the items that valuate to True.

[‘banana’, ‘cherry’, ‘kiwi’, ‘mango’]

Question 32

unary operation

Answer 32

only one value is involved

it can be unary + and Unary -

examples

x =5
y= -3

print(-1.0) # -1
print(-x) # -5

print(-y) # 3

Question 33

string format()

The format() method allows you to format selected parts of a string.

Add a placeholder where you want to display the price:

price = 49
txt = “The price is {} dollars”
print(txt.format(price))

Answer 33

The price is 49 dollars

Question 34

Format the price to be displayed as a number with two decimals:

txt = “The price is {:.2f} dollars”

Answer 34

The price is 49.00 dollars

Question 35

Close the file when you are finish with it:

f = open(“demofile.txt”, “r”)
print(f.readline())
f.close()

Answer 35

Hello! Welcome to demofile.txt

Question 35

To open a file for reading it is enough to specify the name of the file:

Answer 35

f = open(“demofile.txt”)

To open the file, use the built-in open() function.

The open() function returns a file object, which has a read() method for reading the content of the file:

Question 36

f = open(“demofile.txt”, “r”)
print(f.read())

Answer 36

Hello! Welcome to demofile.txt
This file is for testing purposes.
Good Luck!

Question 37

To write to an existing file, you must add a parameter to the open() function:

“a” - Append - will append to the end of the file

“w” - Write - will overwrite any existing content

f = open(“demofile2.txt”, “a”)
f.write(“Now the file has more content!”)
f.close()

Answer 37

Hello! Welcome to demofile2.txt
This file is for testing purposes.
Good Luck!Now the file has more content!

** Open command with ‘a’ attribute opens an existing file and appends to that file.

** w attribute creates a new file and writes to it

Question 38

open and read the file after the overwriting:

Open the file “demofile3.txt” and overwrite the content:

f = open(“demofile3.txt”, “w”)
f.write(“Woops! I have deleted the content!”)
f.close()

f = open(“demofile3.txt”, “r”)
print(f.read())

Answer 38

Woops! I have deleted the content!

Question 39

Create a New File

“x” - Create - will create a file, returns an error if the file exist

“a” - Append - will create a file if the specified file does not exist

“w” - Write - will create a file if the specified file does not exist

Answer 39

Example
Create a file called “myfile.txt”:

f = open(“myfile.txt”, “x”)

Result: a new empty file is created!

Question 40

delete a file

Answer 40

import os
os.remove(“demofile.txt”)

Question 41

Check if File exist:

Answer 41

Check if file exists, then delete it:

import os
if os.path.exists(“demofile.txt”):
os.remove(“demofile.txt”)
else:
print(“The file does not exist”)

Question 42

Delete Folder

Answer 42

os.rmdir()

Question 43

reverse a string

Answer 43

“Hello World”[::-1]

Question 44

What function is used to convert a string to an integer?

Answer 44

Use int to convert strings to integers.

Question 45

Math fabs

Answer 45

Return the absolute value of x.

Question 46

math.fmod(x, y)

Answer 46

function fmod() is generally preferred when working with floats, while Python’s x % y is preferred when working with integers.

Question 47

math.frexp(x)

Answer 47

m is a float and e is an integer such that x == m * 2**e exactly

Question 48

math.isnan(x)

Answer 48

Return True if x is a NaN (not a number), and False otherwise.

Question 49

math.isqrt(n)

Answer 49

Return the integer square root of the nonnegative integer n. This is the floor of the exact square root of n, or equivalently the greatest integer a such that a² ≤ n.

Question 50

date.strftime(format)

Answer 50

Return a string representing the date, controlled by an explicit format string. Format codes referring to hours, minutes or seconds will see 0 values.

Question 51

datetime.weekday()

Answer 51

Return the day of the week as an integer, where Monday is 0 and Sunday is 6. The same as self.date().weekday(). See also isoweekday().

Question 52

random.randrange(start, stop[, step])

Answer 52

Return a randomly selected element from range(start, stop, step).

Question 53

random.shuffle(x)

Answer 53

Shuffle the sequence x in place.

To shuffle an immutable sequence and return a new shuffled list, use sample(x, k=len(x)) instead.

Question 54

random.choice(seq)¶

Answer 54

Return a random element from the non-empty sequence seq. If seq is empty, raises IndexError.

Question 55

random.sample(population, k, *, counts=None)

Answer 55

Return a k length list of unique elements chosen from the population sequence. Used for random sampling without replacement.