# Noemi Cabrera # 15 November 2021 # In this lesson, I learned how to delete files using the os.remove() method, check that a file exists using # os.path.exists, check if a path is a file or directory using os.path.isdir and os.path.isfile. Also, I learned # to handle file exceptions using a try/except statement instead of the previous methods I learned and close a file # despite exceptions using a with statement to open it first. This allows the program to keep running even if an # exception is raised. # I had some difficulties trying to figure out why this notebook said some files/directories didn't exist even though the code for the # examples that I have to run were supposed to be correct. Since this was a problem with the code already provided to me, I do not know # how to fix it.

# ************** DO NOT MODIFY OR ADD ANYTHING TO THIS CODE SEGMENT *********** # ************** Click Edit> Clear All Outputs *********** # ************** This code segment must be run before attempting any of the tasks or examples in this lesson ******************** # ************** This cell is a reset cell to remove (if they exist) the parent_dir and any children or leaves # It prepares the directories and files necessary to run the examples and complete the tasks. # This cell can be run first then all others cells in this notebook can be run, then this cell can be rerun # This is the reset. It uses the import shutil (or shell utility) which you will learn later in the course import os, shutil # shutil = shell utility has an important method called rmtree() # linux does not have an equivalent command! # Navigate to `library` directory (if not already in it) current_path = os.getcwd() print(current_path) if ("content" in current_path): nb_path = current_path.split("content")[0] # nb_path = the 1st item in the split list else: nb_path = current_path print("Changing working dir to directory above parent_dir") os.chdir(os.path.join(nb_path,"content")) current_path = os.getcwd() print("Current working directory:", current_path) if (os.path.exists('parent_dir') == True): shutil.rmtree('parent_dir') os.mkdir('parent_dir') os.chdir('parent_dir') os.mkdir('child1_dir') os.chdir('../') current_path = os.getcwd() print("Current working directory:", current_path) #JG import os # Create a file to be deleted file_path = "parent_dir/tmp_file_to_be_deleted.txt" f = open(file_path, 'w') f.close() # list the content of parent_dir print('Content of "parent_dir" after creating the file:') print(os.listdir("parent_dir")) print() # delete the file os.remove(file_path) # list the content of parent_dir print('Content of "parent_dir" after removing the file') print(os.listdir("parent_dir"))

# ************** DO NOT MODIFY OR ADD ANYTHING TO THIS CODE SEGMENT *********** # ************** This code segment must be run before attempting any of the tasks in this lesson ******************** # It prepares the directories and files necessary to complete the tasks. import os, random, shutil # Navigate to `parent_dir` directory (if not already in it) current_path = os.getcwd() if ("parent_dir" in current_path): nb_path = current_path.split("parent_dir")[0] else: nb_path = current_path print("Changing working dir to parent_dir") os.chdir(os.path.join(nb_path,'parent_dir')) print("Current working directory:", os.getcwd()) # Remove the `files_exercises` directory (if it exists) if('files_exercises' in os.listdir()): print('Removing "files_exercises"') shutil.rmtree('files_exercises') # Create a new directory called `files_exercises` print('Making "files_exercises"') os.mkdir('files_exercises') # Change the working directory to `files_exercises` print('Changing working directory to "files_exercises"') os.chdir('files_exercises') # Display the current working directory to verify you are in the correct location print("Current working directory:", os.getcwd()) # Create 100 text files, the first line of each file is a random number in the range [1000, 9999] print("Creating 100 text files") random.seed(25000) # to get the same random numbers every time the setup runs for i in range(100): file_name = str(i) + ".txt" f = open(file_name, 'w') f.write(str(random.randint(1000, 9999))) f.close() f = open('text_file.txt', 'w') f.write("JG") f.close() # Create 5 directories print("Creating 5 directories") for i in range(1, 6): os.mkdir("dir_"+str(i)) print("Environment setup completed!")

# [ ] Complete the following program to delete the first 10 files inside `files_exercises` (0.txt, 1.txt ... 9.txt) # Make sure the to run the environment setup code before running your own program. import os if ('files_exercises' not in os.getcwd()): print("STOP!!!! Run the environment setup code!") # list the content of `files_exercises` print('Content of "files_exercises" before removing the files') print(os.listdir()) #TODO: delete the first 10 files os.remove("0.txt") os.remove("1.txt") os.remove("2.txt") os.remove("3.txt") os.remove("4.txt") os.remove("5.txt") os.remove("6.txt") os.remove("7.txt") os.remove("8.txt") os.remove("9.txt") # list the content of `files_exercises` print('Content of "files_exercises" after removing the files') print(os.listdir())

# In this code, the os module is used with the word 'path' so that we can check later if a file exists. A printout states # the current working directory using os.getcwd() in the print statement. The the path of ficticious file is stored in # the file_path variable. The if/else statements check if the file exists. If it does, then it checks it's a file. If it's # a file, then it's removed from the directory. Howver, if it doesn't exist, an statement saying so will display. import os.path print("Current working directory:", os.getcwd()) #file_path = "parent_dir/fictitious_file.txt" file_path = "/content/parent_dir/fictitious_file.txt" # Removing a file # Check if the path exists if (os.path.exists(file_path)): if (os.path.isfile(file_path)): os.remove(file_path) else: print("Cannot remove a directory") else: print("path does not exist")

# In this code, the os module is used with the word 'path' so that we can check later if a file exists. A printout states # the current working directory using os.getcwd() in the print statement. Then, the path of parent_dir is stored in # the file_path variable. The if/else statements check if the file exists. If it does, then it checks it's a file. If it's # a file, then it's removed from the directory. Howver, if it doesn't exist, an statement saying so will display. import os.path file_path = "parent_dir" print("Current working directory:", os.getcwd()) #file_path = "parent_dir/fictitious_file.txt" file_path = "/content/parent_dir" # Removing a file # Check if the path exists if (os.path.exists(file_path)): if (os.path.isfile(file_path)): os.remove(file_path) else: print("Cannot remove a directory") else: print("path does not exist")

# # [ ] Write a program to delete all the even numbered files inside `files_exercises` # Make sure to run the environment setup code before running your own program. import os if ('files_exercises' not in os.getcwd()): print("STOP!!!! Run the environment setup code!") #TODO: Your code goes here f_path = "parent_dir" print("Current working directory:", os.getcwd()) f_path = "parent_dir/files_exercises.txt" if (os.path.exists(f_path)): if (os.path.isfile(f_path)): os.remove(f_path[::2]) else: print("Cannot remove a directory") else: print("path does not exist")

# [ ] Write a program to delete all the directories inside `files_exercises` # Make sure the to run the environment setup code before running your own program. import os if ('files_exercises' not in os.getcwd()): print("STOP!!!! Run the environment setup code!") #TODO: Your code goes here f_path = "parent_dir" print("Current working directory:", os.getcwd()) f_path = "parent_dir/files_exercises.txt" if (os.path.exists(f_path)): if (os.path.isfile(f_path)): os.remove(f_path) else: print("Cannot remove a directory") else: print("path does not exist")

# [ ] Write a program to ask the user for a file number, # then delete the file if it exists or display an appropriate error message if it does not. # Make sure the to run the environment setup code before running your own program. # Test your program with the following: # case 1: user inputs 84, 84.txt should be deleted # case 2: user inputs 84 (again), a File does not exist message is printed # case 3: user inputs 5, 5.txt should be deleted import os if ('files_exercises' not in os.getcwd()): print("STOP!!!! Run the environment setup code!") #TODO: Your code goes here f_number = input("Enter a file number: ") f_path = "parent_dir/files_exercises.txt" if (os.path.exists(f_path)): if (os.path.isfile(f_number)): os.remove(f_number) else: print("Error - Cannot remove a directory") else: print("path does not exist")

# In this code, the os.path module is used. The path to fictitious.txt is stored in the file_path variable. # Then, a try & except statement is used to check the different exceptions and allow program to keep executing # despite errors.In this case, the ficticious file is removed from parent_dir because it didn't have any exceptions. import os.path file_path = "/content/parent_dir/fictitious_file.txt" # Remove a file try: os.remove(file_path) except FileNotFoundError as exception_object: print("Cannot find file: ", exception_object) except PermissionError as exception_object: print("Cannot delete a directory: ", exception_object) except Exception as exception_object: print("Unexpected exception: ", exception_object)

# In this code, the os.path module is used. The path to parent_dir is stored in the file_path variable. # Then, a try & except statement is used to check the different exceptions and allow program to keep executing # despite errors.In this case, parent_dir cannot be removed because it's a directory so the unexpected exception # print statement will display. import os.path file_path = "/content/parent_dir" # Remove a file try: os.remove(file_path) except FileNotFoundError as exception_object: print("Cannot find file: ", exception_object) except PermissionError as exception_object: print("Cannot delete a directory: ", exception_object) except Exception as exception_object: print("Unexpected exception: ", exception_object)

# [ ] Write a program to ask the user for a file number, # then delete the file if it exists or display an appropriate error message if it does not. # Use file exception handling instead of file existence tests. # Make sure to run the environment setup code before running your own program. # Test your program with the following: # Case 1: When the user inputs 84, the program should delete the file 84.txt # Case 2: When the user inputs 84 (again), the program should print a File Not Found error message # Case 3: When the user inputs 5, the program should delete the file 5.txt import os if ('files_exercises' not in os.getcwd()): print("STOP!!!! Run the environment setup code!") #TODO: Your code goes here f_number = input("Enter a file number: ") f_path = "parent_dir/files_exercises.txt" try: os.remove(f_number) except FileNotFoundError as exception_object: print("Cannot find file: ", exception_object) except PermissionError as exception_object: print("Cannot delete a directory: ", exception_object) except Exception as exception_object: print("Unexpected exception: ", exception_object)

# In this code, the path to text_file.txt is stored in the file_path variable. Then a try and except statement # is used to open this file. Since an exception was raised, the file coudn't be closed using the regular .close() statement. file_path = "/content/parent_dir/files_exercises/text_file.txt" try: file = open(file_path, 'r') x = int(file.readline()) # Raise an exception if lines are not numeric file.close() # Might never be reached if file.write raised an error except Exception as exception_object: print("Unexpected exception:", exception_object) print("File is closed?", file.closed)

# In this code, the path to text_file.txt is stored in the file_path variable. Then a try and except statement # is used to open this file. In this case, the file did close even though an exception was raised because the # finally clause was used at the end. file_path = "/content/parent_dir/files_exercises/text_file.txt" try: file = open(file_path, 'r') x = int(file.readline()) #raise an exception if lines are not numeric except Exception as exception_object: print("Unexpected exception:", exception_object) finally: file.close() # will be executed whether an exception was raised or not print("File is closed?", file.closed)

# In this code, the path to text_file.txt is stored in the file_path variable. Then a try and except statement # is used to open this file. In this case, the file did close even though an exception was raised because the # with statement was used to open the file. file_path = "/content/parent_dir/files_exercises/text_file.txt" try: with open(file_path, 'r') as file: x = int(file.readline()) #raise an exception if lines are not numeric except Exception as exception_object: print("Unexpected exception", exception_object) print("File is closed?", file.closed)

# [ ] Write a program to print the first line of every file inside `files_exercises` # Use a `with` statement to open (and close) every file # Make sure the to run the environment setup code before running your own program. import os if ('files_exercises' not in os.getcwd()): print("STOP!!!! Run the environment setup code!") #TODO: Your code goes here file_path = "/content/parent_dir/files_exercises" with open(files_exercises, 'r') as file: for line in file: print(line[0]) print("File is closed?", file.closed)