Chapters 1-20

Question 1

What is the command to create a directory in Powershell?

Answer 1

mkdir

Question 2

How would you output the text below in a Python print statement.

That’s a ‘piece of cake’ as they say

Answer 2

print(“That’s a ‘piece of cake’ as they say”)

Question 3

What is the command to run Python from Powershell?

Answer 3

python

Question 4

How do you write a single line comment in Python?

Answer 4

#

Question 5

What data type is 4.0

Answer 5

It’s a float

Question 6

If we execute the statement

x = 4/2
then what is the datatype of x

Answer 6

It’s a float

Question 7

what data type is 4

Answer 7

It’s an int

Question 8

what is the % operator called and what does it do

what is the result of 5 % 2

Answer 8

It’s the modulo operator and displays the remainder portion of a division

5 % 2 is 1

Question 9

What is the order of calculation of the following operators

+ - % / * ( ) **

Answer 9

P
E
(M&D) left to right
(A&S) left to right

(MD)(AS)The actual order is that you do the multiplication and division in one step, from left to right, then you do the addition and subtraction in one step from left to right.

Question 10

What is the exponent operator in Python

Answer 10

**

Question 11

How do you round a floating point number in Python (e.g. 1.73)

Answer 11

round()

round(1.73) gives the answer 2

Question 12

How can we output a variable in the middle of some text in a print statement

e.g.
my_height = 180

print the statement
my height is (my_height) cms

Answer 12

print(f”some text {variable_name} more text”)

print(f”my height is {my_height} cms”)

Question 13

How can we create a string with a variable in it?

Answer 13

f-string can be used to do this

e.g text_to_output = f”my height is {my_height} cms”

The text is substituted in when the command is executed - if the variable subsequently updates to a new value, the f-string is not implicitly updated with the new value

Question 14

How can we create a string with a variable in it that overcomes f string limitation to dynamically update.

Answer 14

Every object has a .format method e.g.

hilarious = False
joke_evaluation=”Is that funny? {}”
joke_evaluation.format(hilarious)

=> ‘Is that funny? False’

If hilarious is updated to True then you get

joke_evaluation.format(hilarious)

=> ‘Is that funny? True’

Question 15

What does the following code do

print(“my name is “,end=’’)
print(“Hans Solo”)

Answer 15

The end = ‘’ argument will not create an auto LF/CR at the end of the print statement.

The second print statement is on the same line as the first.

e.g.
my name is Hans Solo

is output

Using end = ‘ ‘ or end = ‘,’ would place a space or , at the end of the first print statement or any specified delimiter text

Question 16

What is output?

welcome_text = “Welcome to {} in the {}”

print(welcome_text.format(“LA”,”USA”))

print(welcome_text.format(“London”,”UK”))

Answer 16

Welcome to LA in the USA
Welcome to London in the UK

Question 17

What is the code for the following:

1. define x = 43 and y = 51
2. define a variable z to holds the text “You are x degrees of longitude and y degrees of latitude” where x and y are themselves variables
3. print the value of z

Answer 17

x=43
y=45
z=”You are {} degrees longitude and {} degrees of latitude”
print(z.format(x,y))

Question 18

What is the escape sequence that prints a new line e.g. how do we split

print(“line 1 line 2”)

line 1 line 2

so that there is a separate line between them when printed

Answer 18

The escape sequence for new line is \n (backslash n) so

print(“line 1 \nline 2”) gives

line 1
line 2

as output

Question 19

How do we print text across multiple lines in a print statement (not using \n)

E.g so we get :

line 1 followed by line 2
in turn followed by line
line 3
finishing at line 4

Answer 19

Use “”” in the print statement so

print(“"”line 1 followed by line 2
in turn followed by line
line 3
finishing at line 4”””)

Question 20

What is an escape sequence? and how do you put one into a string?

Answer 20

Escape sequences are used in strings for handling difficult-to-type characters.

There are different ways of starting an escape sequence - they can start with single quote - ‘ - double quote - “ - or backslash - .

Question 21

How you would you use an escape sequence to print the sentence with a double quote “ escape character

I am 6’2” tall.

Answer 21

print(“I am 6’2" tall.”)

escape second double quote inside string

I am 6’2” tall.

The escape character tells Python the second double quote is part of the string

Question 22

How you would you use an escape sequence to print the sentence with a single quote ‘ escape character

I am 6’2” tall.

Answer 22

print(‘I am 6'2” tall.’)

escape second quote inside string

I am 6’2” tall.

The escape character tells Python the second single quote is part of the string

Question 23

How can you put a tab into a line of text with an escape sequence

Answer 23

\t

e.g.
“\tI’m tabbed in.”

Question 24

What is the escape character to allow for text to be accepted as a series of lines

Answer 24

””” or ‘’’

e.g.

fat_cat = “””
I’ll do a list:
\t* Cat Food
\t* Fishies
\t* Catnip\n\t* Grass
“””

Question 25

What do the following escape sequences do?

\
'
"
\t
\r

Answer 25

output a

\ - Backslash ()
' - Single-quote(‘)
" - Double-quote(“)
\t - Horizontal tab
\r - Carriage Return

Question 26

What do the following escape sequences do?

\a
\b
\f
\n
\v

Answer 26

output a

\a ASCII bell (BEL)
\b ASCII backspace (BS)
\f ASCII form feed (FF)
\n ASCII line feed (LF)
\v ASCII vertical tab (VT)

Question 27

What do the following escape sequences do?

\uxxxx
\Uxxxxxxxx

Answer 27

output a

\uxxxx - character with a 16-bit hex value
\Uxxxxxxxx - character with a 32-bit hex value

print(“hex 16 gives \u0048\u0065\u006c\u006c\u006f”)
print(“hex 32 gives \U00000048\U00000065\U0000006c\U0000006c\U0000006f”)

gives

hex 16 gives Hello
hex 32 gives Hello

Question 28

What doe the following escape sequence do?

\ooo

e.g.

txt = “\110”

Answer 28

#A backslash followed by three integers will result in a octal value: 
txt = "\110\145\154\154\157" 
print(txt) 

gives result
Hello

Question 29

What doe the following escape sequence do?

\xhh

e.g.
txt =”\x48”

Answer 29

#A backslash followed by an 'x' and a hex number represents a hex value: 
txt = "\x48\x65\x6c\x6c\x6f" 
print(txt) 

gives result
Hello

Question 30

What doe the following escape sequence do?

\N{name}

Answer 30

A backslash followed by an ‘N’ and a character named in the Unicode database will output the named character from UniCode

e.g. print(“Here is the card suit for spades \N{BLACK SPADE SUIT}”)

prints spade symbol

Here is the card suit for spades ♠

Question 31

How do we input a value into a variable ?

e.g. complete the next line
print(“What is your age?”, end=’ ‘)

and capture a variable named age

What does end = ‘ ‘ do?

What will the datatype be?

Answer 31

age = input()

will prompt for a value and capture it as a string (‘str’)

Question 32

How do we capture a value into a variable and issue a prompt in one command / line of code?

Answer 32

a_variable = input(“issue a prompt”)

e.g.
age = input(“How old are you? “)

Question 33

How would you search for python documentation on the input command from within Windows PowerShell

Answer 33

python -m pydoc input

Question 34

what is a script in python?

Answer 34

It’s simply a .py file

Question 35

what does argv do?

Answer 35

argv holds the values of arguments passed in when running a python script

e.g. python ex13.py first 2nd 3rd

use and unpack like this:

from sys import argv
script, first, second, third = argv

note first argument unpacked is the script name and then the arguments passed in

Question 36

What is a module?

Answer 36

Consider a module to be the same as a code library.

A file containing a set of functions you want to include in your application.

You can name the module file whatever you like, but it must have the file extension .py

Question 37

How do you include a module in your python code?

Answer 37

import

e.g. to include functionality from mymodule and use in your script

import mymodule 
mymodule.greeting("Jonathan") 

When using a function from a module, use the syntax: module_name.function_name.

Question 38

How do you create an alias to a module in your code?

Answer 38

Use as

e.g. 
import mymodule as mx 

a = mx.person1[“age”]
print(a)

Question 39

What is a built-in module?

Answer 39

There are several pre-supplied and built-in modules in Python, which you can import whenever you like.

e.g.
import platform

x = platform.system()
print(x)

Question 40

How do you include only a specified part of a module?

Answer 40

You can choose to import only parts from a module, by using the from keyword.

e.g.
The module named mymodule has one function and one dictionary:

def greeting(name):
print("Hello, " + name)

person1 = {
“name”: “John”,
“age”: 36,
“country”: “Norway”
}

Import only the person1 dictionary from the module:

from mymodule import person1

print (person1[“age”])

Note: When importing using the from keyword, do not use the module name when referring to elements in the module. Example: person1[“age”], not mymodule.person1[“age”]

Question 41

How do you close a file in Python?

Answer 41

use the close() command on your file object e.g.

filename = “myfile.txt”
file_object = open(filename)
txt = file_object.read()
file_object.close()

Closing a file has the same action as File … Save in Windows menu

Question 42

How do you read a a single line of file in Python?

Answer 42

use the readline() command on your file object e.g.

filename = "myfile.txt"
file\_handler = open(filename)
txt = file\_handler.readline()

will read and load the contents of the first line of the file into the txt variable

Each time a file_handler.readline() command is issued a line is read from the current seek position until right after the next \n that ends the line.

Question 43

How do you read a file in Python?

Answer 43

use the read() command on your file handler e.g.

filename = "myfile.txt"
file\_handler = open(filename)
txt = file\_handler.read()

will read and load the contents of the file into the txt variable

file_handler = open(filename,’r’) does the same thing - option r (read) is the default option

Question 44

How do you open a file in Python?

Answer 44

use the open() command and associate it with a file handler that we can then issue futher commands to

e.g.

filename = “myfile.txt”

file_handler = open(filename)

Think of a file handler as being like a DVD player - you can issue command to it to manipulate the DVD as required e.g. open, read, read line, find a position, close

Files can be opened by more than one file handler if needed

Question 45

How do you delete a file?

Answer 45

file_handler.truncate()

or open in ‘w’ mode has the effect of truncating (deleting any existing file before writing to a new one).

Question 46

How do you move the read/write location to a specified position in the file and

1 ) print the position in the file

2) read the current line from that position

Answer 46

.seek()

.tell()

.readline()

seek moves the file handler to the specified position (byte). tell confirms the current position. readline reads a line from the file and positions the file handler ‘head’ after the \n that ends the line

f = open("GfG.txt", "r")
print(f.read())
f.seek(20) # sets Reference point to twentieth byte
 # index position from the beginning

print(f.tell()) # prints current position

print(f.readline()) # read fron current position until end of line (\n)
f.close()

Question 47

How do you move the read/write location to the beginning of the file

Answer 47

file_handler.seek(0)

Question 48

How do you open a file to write to it? Name two methods - one to overwrite and one to add to existing file.

Answer 48

file_handler = open(file_to_open,’w’)

w has the effect of truncating deleting any existing file before writing to a new one.

file_handler = open(file_to_open,’a’)

will append and not delete existing file.

Question 49

What is a module in Python?

Answer 49

Consider a module to be the same as a code library - it’s a .py script / file containing a set of functions you want to include in your application.

You can write your own modules and/or use the built-in functions (BIFs) supplied by Python.

Question 50

What is a module in Python?

How do we import a module in Python?

Can we import part of a module?

Answer 50

A module to be the same as a code library - it’s a .py script / file containing a set of functions you want to include in your application.

e.g. Save this code in a file named mymodule.py

def greeting(name):
 print("Hello, " + name)

To use the module it’s simply import

import mymodule
mymodule.greeting("Jonathan")

Note: When using a function from a module, use the syntax: module_name.function_name.

Question 51

What does the from keyword do?

How would you use it?

Answer 51

If we are using a large module with many functions defined in it - we can choose to import only named functions

e.g.

from my_code_library import my_function

from os.path import exists

(os.path is a built in library supplied by Python)

import platform
x = platform.system()
print(x)

Question 52

What can go in a module?

How do you rename a module in your code?

Answer 52

A module can contain functions but also variables of all types (arrays, dictionaries, objects etc)

Use as to rename a module and use it in your code (or alternatively reference it direct by module_name.function_name

import mymodule as mx

a = mx.person1[“age”]
print(a)

Question 53

What does the exists command do? and how do you use it?

Answer 53

Exists returns True if a file exists based on its name in a string as an argument. It returns False if not.

e.g.

from os.path import exists

file_to_create = input(“file name for new file”)

file_exists_check = exists(file_to_create) # check if file exists

Question 54

What does cat do on the Powershell command line?

Answer 54

cat prints the contents of a named file

>cat text.txt

Question 55

How can you create a simple text file from the command line?

Answer 55

> echo “This is a test file.” > test.txt

will create a file named test.txt with the content specified

Question 56

What is a function?

Answer 56

A function is a block of code which only runs when it is called.

You can pass data, known as parameters, into a function.

A function can return data as a result.

Question 57

How do you code a function in Python?

Answer 57

Functions are created using the def keyword followed by brackets for any inputs, then a colon.

After the colon the code to carry out the activity required by the function is written.

e.g.

def my\_function():
 print("Hello from a function")

To call the function it’s

my_function() # will print Hello from a function”

This simple function has no inputs and outputs.

Question 58

How do you pass an unspecified number of arguments into a function (a bit like argv does to scripts)?

Answer 58

Use *args as input parameter

def my\_function(\*args) :
# body of function code goes here

*args tells Python to take all the arguments to the function and put them in args as a list (tuple)

This way the function will receive a tuple of arguments, and can unpack and access the items accordingly

Question 59

How would you write a simple function to print the square and cube of an number input to the function?

Answer 59

def square\_and\_cube\_it(number):
 print(f"""
 Your number is {number}
 Its square is {number\*\*2}
 Its cube is {number\*\*3}
 """)

square_and_cube_it(4)

gives

Your number is 4
Its square is 16
Its cube is 64

Question 60

Can functions have variables? and what is their scope?

Answer 60

Any type of variable can be used in a function. The scope of the variable is local to the function.

Variables that are created outside of a function are known as global variables.

Global variables can be used by everyone, both inside of functions and outside.

def int\_and\_ext():
 c = 10
 print("In function local c = ",c)

c = 5
print(“Before function global c = “, c)
int_and_ext()
print(“After function global c = “, c)

gives the following ouput

Before function global c = 5
a*b*c in function is 60
In function local c = 10
After function global c = 5