Intro to Programming Session 2 -f strings

Question 1

What is string formatting?

Answer 1

Technique used to construct and manipulate strings by inserting variables, values or expressions into predefined placeholders or specificying fromatting rules for data representation within a string

Question 2

String formatting have tools to

Answer 2

control text output and making it look ‘nice’

Question 3

What data type are we looking at this session?

Answer 3

Dictionaries

Question 4

Usually we have seen one way to print combinations of text and data by

Answer 4

joining them together with commas

Question 5

Example 1 of :

Until now we have seen one way to print combinations of text and data: Joining them together with commas:

Answer 5

Question 6

What will this print out?

Answer 6

There were 1022 participant

Question 7

Why does this method of printing combinations of text and data by joining them together with commas seem imprecise?

Answer 7

For example, if you have floating point numbers it’s nice to be able to limit the number of decimal places - or centre things on the screen.

Question 8

Why does this method of printing combinations of text and data by joining them together with commas seem imprecise?

For example, if you have floating point numbers it’s nice to be able to limit the number of decimal places - or centre things on the screen…

Answer 8

Question 9

F strings are also known as

Answer 9

formatted string literals

Question 10

F strings are - (3)

Answer 10

concise and readable way to embed expression inside strings in Python, making it easier to interpolate (insert) variables and expressions directly into the string

They allow for easy string formatting

F strings are prefixed with the letter ‘f’ or ‘F’ (just before quote marks) and contain expressions enclosed in curly braces {}

Question 11

Write a piece of code using f string that stores my_variable with 100, has variable foo with f string saying my variable contains value of 100 and print it

Answer 11

Question 12

What is piece of output of this code?

Answer 12

My variable contains the value 100

Question 13

What does the ‘f’ tell us in this code? - (2)

Answer 13

The ‘f’ tells Python that anything inside curly brackets in the string is a variable -
# it should be

replaced by its value.

Question 14

What is literals? - (3)

Answer 14

Refers to raw data that is written directly into source code such as numbers, strings and Boolean values

Values are not variables and used to represent fixed data types

E.g., 42 is numeric literal, “Hello” is a string literal and True is Boolean literal

Question 15

Write a code using fstrings storing 10 to variable ‘a’, storing 15.0 to variable ‘b’ and c containing string ‘test’

Have a f string stored in variable ‘mystr’ which says ‘My vars are and prints values of c,b,a

Then output f string

Answer 15

Question 16

What is output?

Answer 16

My vars are Test, 15.0, 10

Question 17

The ways in which variables output in f strings depends on

Answer 17

variable type

Question 18

The ways in which variables output in f string depends on variable type

For example… in this code’s output:

Answer 18

the float in this case is shown with a .0 on the end whilst the int is not.

Question 19

f-strings allow us to

Answer 19

format the data nicely as we print it.

Question 20

When using f-strings, you can include formatting options

such as..

Answer 20

placing a colon (:) at end of variable name with some numbers or characters with desired formatting specifications

Question 21

f strings offer ways to format output which includes - (2)

Answer 21

1. Justifying text
2. Formatting Data

Question 22

f strings offer ways to format output which includes justiying the data meaning - (3)

Answer 22

You can specify the width of the field for each variable to ensure consistent spacing in printed output.

By default, f-strings left-align text.

If you want to justify text, you can use < for left justification, > for right justification, and ^ for center justification.

Question 23

f strings offer ways to format output which includes justiying the data for example..

Answer 23

by making sure it takes up a certain amount of space for each variable). This is useful when we want to print tables of data.

Question 24

f strings offer ways to format output which includes formatting the data -

Answer 24

You can format numerical data using various specifiers.

Question 25

f strings offer ways to format output which includes formatting the data - example

Answer 25

for example limiting the number of decimal place in a float or adding zeros to the start of an integer

Question 26

Example of justifying data with f-strings:

If we add ‘:20’ in f strings then it will

Answer 26

force our value to take up a certain amount of space by adding, for instance :20 if we want it to take up 20 spaces.

Question 27

Write a piece of code in which it stores string of ‘Test’ into myvar variable

then print just variable using f string with 3 ‘=’ signs around it

Answer 27

Question 28

What is output of the code?

Answer 28

Question 29

Write a piece of code in which it stores string of ‘Test’ into myvar variable

then print just variable using f string so output looks like this:

Answer 29

Question 30

when you provide a string without specifying any alignment in a formatted string, it will be

Answer 30

left-alligned by default

Question 31

For example, when you provide a string without specifying any alignment in a formatted string, it will be left-aligned by default.

Answer 31

In this example, the string “John” is left-aligned within a space of width 10 characters. Since “John” is 4 characters long, Python adds 6 spaces after “John” to fill the remaining width of 10 characters.

Question 32

Write a piece of code in which it stores string of ‘Test’ into myvar variable

then print just variable using f string with 3 ‘=’ signs around it –> left alligned, right alligned and centre alligned

Answer 32

Question 33

By adding a character before the number, we can change the

Answer 33

alignment of f-string

Question 34

What’s the output?

Answer 34

Question 35

In f strings, if the the specified width is less than the length of the variable, the space expands to

Answer 35

accomodate the variable

Question 36

Example:

In Python f-strings, if the specified width is less than the length of the variable, the space expands to accommodate the entire variable.

Answer 36

Note that even though we asked for a 5 character space, it expanded to the 12 characters which are necessary.

Question 37

Example:

In Python f-strings, if the specified width is less than the length of the variable, the space expands to accommodate the entire variable.

Even works with numbers

Answer 37

Question 38

Exercise:

Print your own name and store it in my var and print it centered in space surrounded by stars like this:

** Alex **

Answer 38

Question 39

We can do lots of things to numbers with f-statements such as - (3)

Answer 39

• useful option for integers is to zero-pad the number.
• Controlling the number of decimal points in floating point numbers
• Utilise scientific notation to deal with very small or large numbers

Question 40

What does zero-pad the number?

Answer 40

means adding 0s before the number to fill the space rather than spaces

Question 41

Example of zero-padding an integer

Answer 41

As an example, we could convert the integer 5 into 005

Question 42

When is zero-pad a number

As an example, we could convert the integer 5 into 005

Answer 42

This is often useful when naming files to make sure that they sort correctly (e.g. if using participant numbers)

Question 43

Write a code that stores number ‘5’ in mynum variable

Then prints it

Then add 3 0s before it

Answer 43

Question 44

Example of using leading zeros (0s that appear before other digits in a numerical value) is useful..

Answer 44

Question 45

How to sort a list and print it?

Answer 45

list_name.sort()
print(list_name)

Question 46

To control the number of decimal places in floating point numbers it is possible to

Answer 46

tune the size of the output by changing both the total number of digits in use and how many come after the decimal point:

Question 47

What would this code produce and why? - (3)

Answer 47

== 10.2190==

In the formatted string {myval:10.4f}, the 10 specifies the total width of the formatted string, and .4f specifies that the number should be formatted with four digits after the decimal point.

Since the number 10.219 has only five characters including the decimal point, it’s padded with spaces to meet the specified width of 10 characters, resulting in three leading spaces before the number.

Question 48

What would be output of this code (ignore second line of code) - (4)

Answer 48

==10.2190==

In the formatted string {myval:7.4f}, the 7 specifies the total width of the formatted string, and .4f specifies that the number should be formatted with four digits after the decimal point.

Since the number 10.219 has a total length of 7 characters, including the decimal point and digits, it doesn’t require any additional padding.

Therefore, no leading spaces are added before the number.

Question 49

What is output of this code and why - bottom - (4)

Answer 49

== 10.22==

In the formatted string {myval:7.2f}, the 7 specifies the total width of the formatted string, and .2f specifies that the number should be formatted with two digits after the decimal point.

Since the number 10.22 has a total length of 6 characters, including the decimal point and digits, it requires 1 leading space to meet the specified width of 7 characters.

Therefore, one leading space is added before the number.

Question 50

Python will round the number if you specify fewer decimal places than the number actually has

• (2)

Answer 50

In Python’s formatting, when you use the f format specifier, you can specify the number of decimal places you want using the notation .nf, where n is the number of decimal places.

For example, if you have the number 10.219 and you format it with :.2f, Python will round it to two decimal places – Output will be 10.22

Question 51

In f string we can use scientific notiation

This is especially useful when dealing with very large or small numbers (e.g. femto-Tesla in MEG). We use the - (2)

Answer 51

e formatting character for this.

We can control the total number of spaces and decimal places in the same way as when we used the f formatting character.

Question 52

Example of using scientific notation in f string

Answer 52

If you have not seen this notation before, you read it as: “1.0 times 10 to the power -6”, i.e. 1.0×10−6 or 1 million.

Question 53

What is the output of this code?

Answer 53

Question 54

What does this code mean? - (3)

The participant ID column will need to be the P plus 3 numbers for the ID. We want the ID zero-padded.

The number of trials column should allow us to have up to 9999 trials, so we should make it 4 characters wide as well.

The reaction time column should have enough space for something like 1999.222 and that three decimal places is sufficient (that is, after all, millisecond resolution which is more than sufficient). This makes us decide that the column should be 8 characters wide.

Answer 54

{part_id:03d}: This formats the part_id variable as an integer (d) with leading zeros (0) and a width of 3 characters as want participant’s ID to be zero-padded. The P before the formatted part_id ensures that it’s prefixed with ‘P’.

{num_trials:4d}: This formats the num_trials variable as an integer (d) with a width of 4 characters. Since you want to allow up to 9999 trials, 4 characters are sufficient.

{rt:8.3f}: This formats the rt variable as a floating-point number (f) with 3 decimal places and a total width of 8 characters. This ensures there’s enough space for the reaction time with millisecond resolution.

Question 55

Fix the code below to output a formatted table line for each participant.

The participant ID column will need to be the P plus 3 numbers for the ID. We want the ID zero-padded.
The number of trials column should allow us to have up to 9999 trials, so we should make it 4 characters wide as well.
The reaction time column should have enough space for something like 1999.222 and that three decimal places is sufficient (that is, after all, millisecond resolution which is more than sufficient). This makes us decide that the column should be 8 characters wide.

:
| P{part_id:03d} | {num_trials:3d} | {rt:8.3f} |

P{part_id:03d} | {num_trials:3d} | {rt:8.3f} |

Answer 55

Used the loop index i to access elements from part_ids, trial_counts, and rts.
Used correct index i to access the elements from each list.
Applied correct formatting for participant ID (:03d), trial counts (:4d), and reaction time (:8.3f).

Question 56

We often want to ask the user for information. One to do this is the

Answer 56

input () function in Python