String Manipulation #

In this lab we are going to explore lots of ways to manipulate strings with Python.

Syllabus Topics [HL & SL] #

B2.1.2 Construct programs that can extract and manipulate substrings.
B2.3.2 Construct programs utilizing appropriate selection structures.
B2.3.3 Construct programs that utilize looping structures to perform repeated actions.

Key Vocabulary #

Term	Definition
Variable	A named storage location in a computer’s memory that can hold a value. The value can change during the execution of a program.
Initialize	The process of giving a variable its very first value when it is created.
Assign	To give a variable a new value after it has been initialized.
Data Type	A classification that specifies which type of value a variable can hold, such as a char, string, int, or a boolean (true/false) value. It determines the operations that can be performed on the data.
Char	A data type. Short for character, it’s a single letter, number, symbol, or space. A string is made up of multiple characters.
String	A data type. A sequence of characters, such as letters, numbers, and symbols, treated as a single piece of text.
Substring	A continous string of characters within a string
Slicing	The process of extracting a portion of a string using `[start:stop]`
Concatenation	Joining strings together using `+`

[0] Set up #

💻 Go to your dpcs/unit00_strings folder.

cd ~/desktop/dpcs/unit00_strings/

💻 Clone your repo. This will copy it onto your computer.

git clone https://github.com/isf-dp-cs/lab_string_manipulation_yourgithubusername

Below you’ll see that the git clone command has yourgithubusername.
You need to replace this with your username
e.g. https://github.com/isf-dp-cs/lab_string_manipulation_brittegenzlinger

💻 In the Terminal, type the following command to open the lab folder.

cd lab_string_manipulation_yourgithubusername

💻 Enter the Poetry Shell to start the lab. As a reminder, we will run this command at the start of each lab, but only when we are inside a lab folder.

poetry shell

👾 💬 Exiting the poetry shell
When you want to exit the shell, you can type exit or ^D

[1] String Methods #

Star Tree 🌲 #

Concatenate and Multiply Strings ↕

You can concatenate (combine) strings using +.

"tree" + "house"
>>> "treehouse"

You can multiply strings using *:

"why" + "y"*5
>>> "whyyyyyy"

💻 In star_tree.py, write code that prints out * in a tree pattern.

The height of the tree should be determined by user input. For example:

How tall is the tree? 
>>> 4

   *
  ***
 *****
*******

How tall is the tree? 
>>> 2

 *
***

Abracadabra #

Slicing ↕

You can get a substring using slicing. Just like for loops, the start index is inclusive and the end index is exclusive.

my_string = "hello world!"

my_string[1:6]
  >>> "ello "
my_string[4:7]
  >>> "o w"

If you leave one of the numbers blank, it includes everything.

my_string[1:]
  >>> "ello world!"
my_string[:3]
  >>> "hel"
my_string[:]
  >>> "hello world!"

💻 In abracadabra.py, write code that prints out a word in a triangle pattern. The user should input the word. For example:

Tell me a word and I'll show you a trick: abracadabra
           
          a
         ra
        bra
       abra
      dabra
     adabra
    cadabra
   acadabra
  racadabra
 bracadabra
abracadabra

Tell me a word and I'll show you a trick: Huh?
    
   ?
  h?
 uh?
Huh?

camelCase 🐪 #

upper() and lower() ↕

Python has built-in functions to convert strings to upper case or lower case.

my_string = "Hello World!"

my_string.upper()
  >>> "HELLO WORLD!"
my_string.lower()
  >>> "hello world!"

split() ↕

.split()converts a string into a list of sub-strings. By default, it splits on spaces

my_string = "Wow! Why are camels so fast?"
word_list = my_string.split()
word_list
  >>> ['Wow!', 'Why', 'are', 'camels', 'so', 'fast?']

If you give a specific character as a parameter, it will split on that character instead:

poem = "But still; like dust; I’ll rise."
poem_list = poem.split(";")
poem_list
  >>> ['But still', ' like dust', ' I’ll rise.']

When naming your variables, it can be inconvenient that you can’t use spaces. To solve this problem, programmers have come up with a few standard naming conventions:

snake_case is commonly used by Python programmers, since it’s used in Python’s built-in functions:

# snake_case
number_of_donuts = 34

camelCase is commonly used by Java, JavaScript, and TypeScript programmers:

# snake_case
numberOfDonuts = 34

There are also other less common options, such as PascalCase and kebab-case.

💻 In the file snake_to_camel.py, write code that can convert a snake_case variable into camelCase variable. For example

Variable name: number_of_donuts
           
numberOfDonuts

[2] ANSI Codes #

ANSI escape codes are special codes that you can concatenate onto strings to change the formatting when you print to the console.

yellow_bg = "\u001b[43;1m" # code for a yellow background
reset_code = "\u001b[0m" # code to set formatting back to normal
print(yellow_bg + "the sun is yellow" + reset)

Standard Text Colors click to expand ⬇️

code	description	code	description
`\u001b[30m`	Black font color	`\u001b[30;1m`	Bright Black font color
`\u001b[31m`	Red font color	`\u001b[31;1m`	Bright Red font color
`\u001b[32m`	Green font color	`\u001b[32;1m`	Bright Green font color
`\u001b[33m`	Yellow font color	`\u001b[33;1m`	Bright Yellow font color
`\u001b[34m`	Blue font color	`\u001b[34;1m`	Bright Blue font color
`\u001b[35m`	Magenta font color	`\u001b[35;1m`	Bright Magenta font color
`\u001b[36m`	Cyan font color	`\u001b[36;1m`	Bright Cyan font color
`\u001b[37m`	White font color	`\u001b[37;1m`	Bright White font color

256 Text Colors click to expand ⬇️

code	description
`\u001b[38;5;` + n + `m`	Standard font color where `n` can be a number between 0-7
`\u001b[38;5;` + n + `m`	High intensity font color where `n` can be a number between 8-15
`\u001b[38;5;` + n + `m`	Rainbow font color where `n` can be a number between 16-231
`\u001b[38;5;` + n + `m`	Gray font color where `n` can be a number between 232-255

Standard Background Colors click to expand ⬇️

code	description	code	description
`\u001b[40m`	Black background color	`\u001b[40;1m`	Bright Black background color
`\u001b[41m`	Red background color	`\u001b[41;1m`	Bright Red background color
`\u001b[42m`	Green background color	`\u001b[42;1m`	Bright Green background color
`\u001b[43m`	Yellow background color	`\u001b[43;1m`	Bright Yellow background color
`\u001b[44m`	Blue background color	`\u001b[44;1m`	Bright Blue background color
`\u001b[45m`	Magenta background color	`\u001b[45;1m`	Bright Magenta background color
`\u001b[46m`	Cyan background color	`\u001b[46;1m`	Bright Cyan background color
`\u001b[47m`	White background color	`\u001b[47;1m`	Bright White background color

256 Background Colors click to expand ⬇️

code	description
`\u001b[48;5;` + n + `m`	Standard background color where `n` can be a number between 0-7
`\u001b[48;5;` + n + `m`	High intensity background color where `n` can be a number between 8-15
`\u001b[48;5;` + n + `m`	Rainbow background color where `n` can be a number between 16-231
`\u001b[48;5;` + n + `m`	Gray background color where `n` can be a number between 232-255

Other Styles click to expand ⬇️

code	description
`\u001b[0m`	Reset all styles
`\u001b[1m`	Bold
`\u001b[4m`	Underline
`\u001b[5m`	Blinking
`\u001b[7m`	Reversed

Formatting Text #

💻 Open up ansi_test.py and complete all 4 TODO: tasks

Add some more color codes
Add color to the poem
Give each letter a different color
Print a grid of every possible background color (0-255)
Hint: the 256 Background Colors follow a simple forumula: \u001b[48;5; + n + m

[3] Deliverables #

⚡✨ Once you complete the lab, be sure to complete these two steps:
📋 Update Syllabus Tracker
These are the topics covered in this lab:
B2.1.2 Construct programs that can extract and manipulate substrings.
B2.3.2 Construct programs utilizing appropriate selection structures.
B2.3.3 Construct programs that utilize looping structures to perform repeated actions.
Go to your Syllabus Content Checklist in your Google Drive and update it accordingly.
💻 Push your work to Github
git status
git add -A
git status
git commit -m "describe your code here"
git push
git remote

[4] Extension #

Print Vertical #

💻 In print_vertical.py, write code that takes a sentence and prints it vertically. The user should input the sentence. For example:

Enter your text: how are you doing today?

haydt
orooo
weuid
   na
   gy
    ?

Enter a string: When I was a youthful lad...

WIwayl
h a oa
e s ud
n   t.
    h.
    f.
    u 
    l