28 Python Cheat Sheet

28.1 Data Structure Initialization

my_list = []
my_tuple = ()
my_dict = {}

28.2 Basic Operations and Data Types

Function/Method	Example Application	Explanation
`print()`	`print("String")` `my_name = "Bram"` `print(my_name)`	Displays the value inside its parentheses on the screen.
`len()`	`my_name = "Bram"` `length_name = len(my_name)` `print(length_name)`	Counts the number of characters in a string.
`input()`	`my_name = input()` `my_name = input("name:")`	Reads a string from standard input.
`str()`	`grade = 9.8` `string_grade = str(grade)`	Converts a specific variable into a string.
`int()`	`grade = 9.8` `int_grade = int(grade)`	Converts a specific variable into an integer.
`float()`	`grade = 9` `float_grade = float(grade)`	Converts a specific variable into a float.
`range()`	`for i in range(1,10):` `print(i)`	Generates a sequence of numbers within a specified range.

28.3 String Manipulation

Function/Method	Example Application	Explanation
`upper()`	`spam = "laptop"` `spam = spam.upper()`	Converts all letters in the string to uppercase.
`lower()`	`spam = "LAPtop"` `spam = spam.lower()`	Converts all letters in the string to lowercase.
`islower()`	`spam = "LAPtop"` `check = spam.islower()`	Returns True when all letters are lowercase, otherwise False.
`isupper()`	`spam = "LAPTOP"` `check = spam.isupper()`	Returns True when all letters are uppercase, otherwise False.
`isalpha()`	`spam = "laptopfromJohnny"` `check = spam.isalpha()` `print(check)`	Returns True if the string consists only of letters and isn’t blank.
`isalnum()`	`spam = "laptopfromBOB789"` `check = spam.isalnum()` `print(check)`	Returns True if the string consists only of letters and numbers and is not blank.
`isdecimal()`	`spam = "888888"` `check = spam.isdecimal()` `print(check)`	Returns True if the string consists only of numeric characters and is not blank.
`isspace()`	`spam = " \n"` `check = spam.isspace()` `print(check)`	Returns True if the string consists only of spaces, tabs, and newlines and is not blank.
`istitle()`	`spam = "De Title Van Het Boek"` `check = spam.istitle()` `print(check)`	Returns True if the string consists only of words that begin with an uppercase letter followed by only lowercase letters.
`startswith()`	`spam = "De Title Van Het Boek"` `check = spam.startswith("De")` `print(check)`	Returns True if the string value called on, begins with the string passed to the method.
`endswith()`	`spam = "De Title Van Het Boek"` `check = spam.endswith("ek")` `print(check)`	Returns True if the string value they are called on ends with the string passed to the method.
`join()`	`my_list = ["My", "name", "is", "Alberto"]` `sentence = ' '.join(my_list)` `print(sentence)`	Joins strings together with a specified separator.
`split()`	`my_sentence = "My name is Alberto"` `the_list = my_sentence.split()` `print(the_list)`	Splits a string into a list of substrings based on a separator.
`partition()`	`my_sentence = "My name is Alberto"` `the_list = my_sentence.partition("is")` `print(the_list)`	Splits a string into three parts based on a separator.
`rjust()`	`my_name = 'Alberto'` `print_name = my_name.rjust(40)` `print(print_name)`	Right-aligns a string within a specified width.
`ljust()`	`my_name = 'Alberto'` `print_name = my_name.ljust(40)` `print(print_name)`	Left-aligns a string within a specified width.
`center()`	`my_name = 'Alberto'` `print_name = my_name.center(40)` `print(print_name)`	Centers a string within a specified width.

28.4 Random

Function/Method	Example Application	Explanation
`random.randint()`	`(import random)` `r = random.randint(1, 100)` `print(r)`	Generates a random integer within a specified range.
`random.choice()`	`(import random)` `my_list = ['Boom', 'Huis', 'Auto']` `choice = random.choice(my_list)` `print(choice)`	Selects a random element from a list.
`random.shuffle()`	`(import random)` `my_list = ['Boom', 'Huis', 'Auto']` `random.shuffle(my_list)` `print(my_list)`	Shuffles the elements in a list randomly.
`random.sample()`	`(import random)` `my_list = ['Boom', 'Huis', 'Auto']` `shuffled_list = random.sample(my_list, len(my_list))` `print(my_list)` `print(shuffled_list)`	Generates a random sample from a list without replacement.

28.5 Lists

Function/Method	Example Application	Explanation
`index()`	`my_list = ['Boom', 'Huis', 'Auto']` `x = my_list.index('Huis')`	Returns the index of the first occurrence of an item in a list.
`enumerate()`	`my_list = ['Boom', 'Huis', 'Auto']` `for i, value in enumerate(my_list):` `print(f"{i}: {value}")`	Adds a counter to an iterable and returns it as an enumerate object.
`append()`	`my_list = ['Boom', 'Huis']` `my_list.append('Auto')` `print(my_list)`	Adds an item to the end of a list.
`list()`	`letter_list = list(dict.keys())`	Converts a dictionary’s keys into a list.
`insert()`	`my_list = ['Boom', 'Huis']` `my_list.insert(1, 'Auto')` `print(my_list)`	Inserts an item at a specified position in a list.
`remove()`	`my_list = ['Boom', 'Huis', 'Auto']` `my_list.remove('Huis')` `print(my_list)`	Removes the first occurrence of an item from a list.
`sort()`	`my_list = ['Boom', 'Huis', 'Auto']` `my_list.sort()` `print(my_list)`	Sorts a list in ascending order.
`reverse()`	`my_list = ['Boom', 'Huis', 'Auto']` `my_list.reverse()` `print(my_list)`	Reverses the elements of a list in place.

28.6 Dictionaries

Function/Method	Example Application	Explanation
`update()`	`my_dict = {'color1': 'Red', 'color2': 'Green'}` `my_dict.update({'color3': 'Blue'})` `print(my_dict)`	Updates a dictionary with elements from another dictionary.
`values()`	`my_dict = {'color1': 'Red', 'color2': 'Green', 'color3': 'Blue'}` `for v in my_dict.values():` `print(v)`	Returns a view of the values in a dictionary.
`items()`	`my_dict = {'color1': 'Red', 'color2': 'Green', 'color3': 'Blue'}` `for i in my_dict.items():` `print(i)`	Returns a view of the key-value pairs in a dictionary.
`keys()`	`my_dict = {'color1': 'Red', 'color2': 'Green', 'color3': 'Blue'}` `for k in my_dict.keys():` `print(k)`	Returns a view of the keys in a dictionary.
`get()`	`my_dict = {'color1': 'Red', 'color2': 'Green', 'color3': 'Blue'}` `color4 = my_dict.get('color4', 'D.N.E.')` `print(color4)`	Returns the value for a specified key if key is

28.7 Files

Function/Method	Example Application	Explanation
`Path()`	`from pathlib import Path` `filePath = Path('Boom', 'Huis', 'Auto')` `print(filePath)`	Creates a file path object.
`path.home()`	`from pathlib import Path` `print(Path.home())`	Retrieves the home directory path.
`os.makedirs()`	`import os` `os.makedirs('C:\Basisbeginselen programmeren\Test')`	Creates a new directory path.
`mkdir()`	`from pathlib import Path` `Path(r'C:\Basisbeginselen programmeren\Test2').mkdir()`	Makes a directory from a Path object.
`path.cwd()`	`from pathlib import Path` `print(Path.cwd())`	Retrieves the current working directory path.
`open()`	`openFile = open(Path(r'C:\DAP') / 'textfile.txt')`	Opens a file for reading or writing.
`read()`	`openFile = open(Path(r'C:\DAP') / 'textfile.txt')` `content = openFile.read()` `print(content)`	Reads the entire content of a file.
`readlines()`	`openFile = open(Path(r'C:\DAP') / 'textfile.txt')` `content = openFile.readlines()` `print(content)`	Reads the file content line by line.
`close()`	`openFile.close()`	Closes an opened file.
`write()`	`openFile = open(Path(r'C:\DAP') / 'textfile.txt', 'w')` `openFile.write('Hoi')` `openFile.close()`	Writes content to a file.
`shutil.copy()`	`import shutil` `file = Path(r'C:\DAP') / 'TextFile.txt'` `copy = Path(r'C:\DAP') / 'COPY_TextFile.txt'` `shutil.copy(file, copy)`	Copies a file to a new location.
`shutil.copytree()`	`import shutil` `folder = Path(r'C:\DAP')` `folder2 = Path(r'C:\DAP_COPY')` `shutil.copytree(folder, folder2)`	Copies an entire directory to a new location.
`shutil.move()`	`import shutil` `folder = Path(r'C:\DAP2\DAP_COPY') / 'TextFile.txt'` `folder2 = Path(r'C:\Basisbeginselen programmeren')` `shutil.move(folder, folder2)`	Moves a file or directory to a new location.