File Handling in Programming
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Questions and Answers

What is the primary purpose of saving data to a file in a program?

  • To improve data security.
  • To allow for simultaneous data entry by users.
  • To retain data between program executions. (correct)
  • To enhance the speed of data processing.

Which step is NOT part of the standard three steps when a program uses a file?

  • Read the data. (correct)
  • Close the file.
  • Open the file.
  • Process the file.

What type of file contains data encoded as text and can be opened in a text editor?

  • Image file.
  • Binary file.
  • Text file. (correct)
  • Executable file.

In which access method is data read sequentially from beginning to end?

<p>Sequential access. (C)</p> Signup and view all the answers

What is the purpose of the open function in file handling?

<p>To open a file and associate it with a file object (D)</p> Signup and view all the answers

What does a filename extension indicate?

<p>The type of data stored in the file (D)</p> Signup and view all the answers

What must be done after a program has finished processing a file?

<p>The file must be closed. (D)</p> Signup and view all the answers

Which of the following statements is true about binary files?

<p>They store data intended only for program use. (B)</p> Signup and view all the answers

How is data written to a file using a file object?

<p>By using the file_variable.write() method (A)</p> Signup and view all the answers

What happens to the data stored in RAM once a program stops running?

<p>Data is deleted. (B)</p> Signup and view all the answers

What happens if the filename does not contain a path when using the open function?

<p>The file is assumed to be in the same directory as the program. (B)</p> Signup and view all the answers

Which symbol is used to denote a raw string in file paths?

<p>r (C)</p> Signup and view all the answers

Which method would require waiting to read specific data stored in a large file?

<p>Sequential access. (D)</p> Signup and view all the answers

What should you do with a file object after finishing its use?

<p>Ensure it is closed using close() method (D)</p> Signup and view all the answers

What does the write method of a file object do?

<p>Writes data to the file (D)</p> Signup and view all the answers

In which mode would you open a file for writing new data?

<p>'w' (B)</p> Signup and view all the answers

What is the purpose of the read method in file handling?

<p>To read the entire contents of a file into memory (A)</p> Signup and view all the answers

What does the readline method return?

<p>A line from the file, including a newline character (C)</p> Signup and view all the answers

What will happen when a file is opened in 'w' mode and it already exists?

<p>The existing file will be overwritten (B)</p> Signup and view all the answers

How can you append data to an existing file without erasing its current contents?

<p>Use 'a' mode for opening the file (B)</p> Signup and view all the answers

What method would you use to remove a newline character from the end of a string?

<p>rstrip (A)</p> Signup and view all the answers

What must you do when writing a string to a file to ensure that it appears on a new line?

<p>Concatenate a ' ' character to the string (C)</p> Signup and view all the answers

What will occur if you fail to remove the newline character from a string read from a file?

<p>An extra blank line will appear in the output (B)</p> Signup and view all the answers

What signifies the position of the next item to be read from a file?

<p>Read position (D)</p> Signup and view all the answers

What must be used to convert numeric values to a string before writing to a file?

<p>str function (B)</p> Signup and view all the answers

Which method is commonly used to determine the end of a file during reading?

<p>readline method (C)</p> Signup and view all the answers

When a program needs to perform mathematical operations on numbers read from a file, what type conversion must be done?

<p>Convert them to numeric types (D)</p> Signup and view all the answers

What is required when working with records in a file?

<p>Add, display, modify, search, and delete records (D)</p> Signup and view all the answers

What does the traceback provide when an exception occurs?

<p>Information about the line numbers causing the error (C)</p> Signup and view all the answers

In a try/except statement, what happens if no exception is raised?

<p>Handlers are skipped (C)</p> Signup and view all the answers

What should an except clause without a specific exception type do?

<p>Handle any type of exception raised (C)</p> Signup and view all the answers

What is the purpose of the finally clause in a try/except statement?

<p>To clean up resources regardless of exceptions (B)</p> Signup and view all the answers

Which exception cannot be avoided even with careful coding?

<p>FileNotFoundError (C)</p> Signup and view all the answers

What is the first step in handling exceptions in Python?

<p>Write a try block (D)</p> Signup and view all the answers

Which statement correctly describes how to format a for loop for reading lines in a file?

<p>for line in file_object: (D)</p> Signup and view all the answers

What kind of data structure is a record considered?

<p>Set of data describing one item (B)</p> Signup and view all the answers

What function should be used to convert a string representing a number to an integer?

<p>int (D)</p> Signup and view all the answers

What must occur first when a program intends to use a file?

<p>Open the file (B)</p> Signup and view all the answers

Which type of file can have its data viewed using a text editor?

<p>Text file (C)</p> Signup and view all the answers

In sequential access to a file, what must occur to reach the last piece of data?

<p>Fast-forward over all previous data (A)</p> Signup and view all the answers

What is the final step after a program has finished using a file?

<p>Close the file (B)</p> Signup and view all the answers

What best describes a binary file's contents?

<p>Not intended to be read by humans (A)</p> Signup and view all the answers

What can happen to data stored in RAM when a program stops running?

<p>It is lost (A)</p> Signup and view all the answers

What is the primary role of an input file within a program?

<p>To provide data for processing (C)</p> Signup and view all the answers

Which of the following correctly describes how text files store numeric values?

<p>As a series of characters (B)</p> Signup and view all the answers

What is the primary role of a file object in file handling?

<p>It provides a way for a program to interact with the data in the file. (A)</p> Signup and view all the answers

What is the effect of using the 'w' mode when opening a file?

<p>It creates a new file or truncates an existing file to zero length. (C)</p> Signup and view all the answers

How should the path be specified in the open function to ensure it is treated as a raw string?

<p>By prefixing it with the letter r. (C)</p> Signup and view all the answers

Which method is used to write data to a file using a file object?

<p>file_variable.write(string) (A)</p> Signup and view all the answers

What happens if a file is opened without specifying a complete path in the filename?

<p>The program assumes the file is in the same directory as the program. (A)</p> Signup and view all the answers

What should you always do after you finish working with a file object?

<p>Close the file using the close method. (B)</p> Signup and view all the answers

Which of the following file extensions indicates that the file contains an image?

<p>.jpg (C)</p> Signup and view all the answers

What is a common misconception about how data is written to a file?

<p>Data can only be written in the 'r' mode. (C)</p> Signup and view all the answers

What happens to the contents of a file when opened in 'w' mode if the file already exists?

<p>The existing contents are overwritten. (A)</p> Signup and view all the answers

Which method is used to read an entire file's content into memory?

<p>read (C)</p> Signup and view all the answers

What is the purpose of the rstrip method when reading strings from a file?

<p>To strip specific characters from the end. (A)</p> Signup and view all the answers

When you append data to an existing file using 'a' mode, what is true about the existing file?

<p>It remains unchanged except for the new data added. (B)</p> Signup and view all the answers

What is the correct way to ensure each data item appears on a new line when writing to a file?

<p>Concatenate a newline character to each data item before writing. (C)</p> Signup and view all the answers

What results from using the readline method on a file?

<p>It reads and returns a single line, including the newline character. (C)</p> Signup and view all the answers

What is a potential issue when reading data from a file without stripping newline characters?

<p>Extra blank lines will appear in the output. (B)</p> Signup and view all the answers

Which of the following correctly describes the read position in a file?

<p>It marks the location of the next item to be read from a file. (D)</p> Signup and view all the answers

What method is used to read a single line from a file until the end of the file is reached?

<p>readline (C)</p> Signup and view all the answers

Which function is used to convert a string to a numeric value when performing mathematical operations?

<p>int (A), float (D)</p> Signup and view all the answers

What is the primary purpose of an exception handler in Python?

<p>To execute specific precautions when exceptions occur (B)</p> Signup and view all the answers

What does the else clause in a try/except statement do?

<p>Executes if no exception was raised (D)</p> Signup and view all the answers

What happens if an exception specified in an except clause does not occur in the try suite?

<p>The program continues without executing the handler (B)</p> Signup and view all the answers

When processing records, what action is NOT typically performed?

<p>Encryption of records (D)</p> Signup and view all the answers

In a try/except statement, what is the purpose of the finally clause?

<p>To ensure cleanup actions are performed regardless of exceptions (C)</p> Signup and view all the answers

What should be done before writing numeric values to a file?

<p>Convert the numbers to strings (B)</p> Signup and view all the answers

What can the try suite contain when an exception may be raised?

<p>Any statements that could cause an error (D)</p> Signup and view all the answers

What is the role of the readline method when reading large files?

<p>Reads one line at a time until the end is reached (D)</p> Signup and view all the answers

Which of the following describes an exception?

<p>An error that occurs while a program is running (C)</p> Signup and view all the answers

What happens when the except clause does not list a specific exception?

<p>It will handle any exception not caught by previous clauses (B)</p> Signup and view all the answers

What method allows a Python programmer to loop through each line in a file automatically?

<p>for line in file_object (D)</p> Signup and view all the answers

Flashcards

File

A location on a computer's storage that stores data.

Writing Data to File

Saving data on a computer file storing for later use.

Reading Data

Retrieving data from a computer file

Text File

File storing data represented as text (like words, numbers).

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Binary File

File storing data as raw, non-text characters.

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Sequential Access

Reading data from a file from the beginning and continuing.

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Opening a File

Establishing connection between program and File.

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Closing a File

Disconnecting the File from the program

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Reading entire file

The read method reads the entire content of a file into memory as a string.

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Reading a line

The readline method reads a single line from a file.

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Read position

The location in the file where the next item will be read.

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Direct Access File

Allows accessing any data point in a file directly, like a music player.

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File Extension

Short characters after a "." that show the file's data type.

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Newline character

The character \n that indicates the end of a line in a text file.

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Append mode (a)

Opens a file to add data to the end; does not overwrite existing content.

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File Object

An object for working with a file.

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Open Function

Opens a file, creating a file object to read/write.

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Write mode (w)

Opens a file to write data; overwrites the existing content if it exists.

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rstrip method

Removes trailing characters (like '\n') from a string.

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File Mode

'r'(read), 'w'(write), or 'a'(append), indicating file operation.

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File object methods

Methods like read(), readline(), used to interact with a file.

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File Location (Path)

Specifies where the file is located on the computer.

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File Object's Write Method

Writes data into a file. Use file_object.write().

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File Close Method

Closes the file connection. Use file_object.close().

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Converting numbers to strings

To store numeric values in a file, the numbers must first be converted into strings.

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Reading numbers from files

Data read from text files will be strings and must be converted to numeric types to do math.

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Sentinel value

An empty string or specific value acts as a marker to signal the end of input in a file.

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Python's for loop for files

Reads lines automatically from a file, ending when the end of the file is found, without using readline() in a loop.

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Record

A set of data describing a single item.

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Sequential access file

Data in a file is written and read in a specific order, one after the other.

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Handling exceptions

Code to handle errors that might occur, preventing crashes.

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Exception

An error that occurs during program execution, often forcing a stop.

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Traceback

The error message showing the line of code causing the exception(error).

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Exception handler

Code that deals with exceptions and helps the program continue running.

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try/except

A block of code used to catch and handle potential errors.

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else clause (in try/except)

Code to execute if no exceptions occur within the try block.

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finally clause

Code that runs regardless of exceptions, used for cleanup.

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Exception object

An object created when an exception is thrown, containing error details.

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Why use files?

Files allow programs to store data persistently, meaning the data remains accessible even after the program ends, unlike variables which disappear when a program finishes.

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Output File

A file where a program writes data. It's like a digital container for storing the program's results.

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Input File

A file from which a program reads data. It's like a source of information for the program.

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Open, Process, Close

These three steps are crucial when working with files: open a connection to the file for reading or writing, process the data, and then close the connection after you're done.

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Text vs Binary

Text files store data as human-readable characters, while binary files store data in a format only computers understand. Text files are like readable stories, while binary files are like encoded messages.

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Try-Except Block

A code block that helps handle potential exceptions, allowing your program to gracefully deal with errors and avoid crashing.

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How to specify the location of a file?

If you want to open a file that is not in the same directory as your program, you need to specify the complete path to the file. This path includes all the folders and subfolders leading to the file.

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Write Method

A function used to send data from your program to a file. It takes the data as a string and writes it to the file.

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Close Method

A function that closes the connection between your program and a file. This is important to release the file and ensure changes are saved.

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What is 'r' mode in opening a file?

It opens a file for reading only. You can access the file's content but cannot modify it.

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What is 'w' mode in opening a file?

It opens a file for writing. If the file exists, its content gets overwritten. If the file doesn't exist, a new file is created.

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Write to a File

Using the 'write' method to save data to a file, like writing information to a document. The data goes into the designated file.

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Read Data from a File

Using the 'read' method to access and get the contents of a file, similar to reading the text from a book.

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Strip Newline Character

Using the 'rstrip' method to remove the newline ( ) character from a string, which is used to denote the end of a line. This cleans up the data and makes it look nicer.

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Append Data

Using the 'a' mode when opening a file to add new data to the end of an existing file, without deleting the original content.

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Concatenate Newline

Adding a newline character (' ') to a string using the '+' operator. This is used to separate data when writing to a file.

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Overwrite vs. Append

'w' mode overwrites the entire file content, replacing it with new data, while 'a' mode appends data to the end of the file, keeping original content.

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Study Notes

Starting Out with Python - Chapter 6: Files and Exceptions

  • This chapter covers files and exceptions in Python
  • Topics include file input/output, using loops to process files, handling records, and the role of exceptions.
  • User input data typically needs to be saved for repeated use across program runs.
  • Files provide a means to persist data between program runs, which is stored on the computer's file system. Data stored in RAM is lost when the program terminates.

Introduction to File Input and Output

  • Storing data in files allows programs to retain data between sessions.
  • Data is stored on the computer's file system.
  • Retained data is retrievable for later use.
  • Two main types of files: text and binary

Writing Data on File

  • Output file: stores program output. This file stores data copied from RAM.
  • Data is copied from RAM (Random Access Memory) to the file.
  • Example data in a file includes pay rate, employee ID, and employee name. Data is written to files as strings, but numbers must be converted.

Reading Data From File

  • Reading data from a file retrieves data stored on the computer's file system.
  • Input file: the file from which data is read.
  • Data is copied from the file to RAM.

Three Steps When a Program Uses a File

  • Open the file: Establishing a connection between the program and the file. This involves creating an object linked to the file.
  • Process the file: The program reads/writes to the file. Using methods like write() to write, and read() to read
  • Close the file: The program disconnects from the file, releasing resources. This is important for proper data handling and preventing data loss.

Types of Files and File Access Methods

  • Two main file types: text and binary files.
  • Text File: Data encoded as text (ASCII or Unicode). Consists of a series of characters.
  • Binary File: Contains data that has not been converted to text. Only meant for programs to read. Cannot be opened and viewed using a text editor.
  • Sequential access: File is read from start to finish, with no ability to skip sections. This is similar to reading a cassette tape.
  • Direct access: The program can move directly to any part of the file. This is similar to using a CD player or an MP3 player, where you can jump to any desired song.

Filenames and File Objects

  • Filename extensions: Short sequences of characters at the end of a file name. Indicate the type of data in the file. Example: .jpg, .txt, .docx.
  • File object: Represents the file in a program. Enables access and processing of the file's data. Python uses objects to work with files.

Opening a File

  • The open function opens files
  • It creates a file object linked to a specific file on the disk
  • file object = open(filename, mode)
    • mode: Specifies read ('r'), write ('w'), or append ('a') operations.
    • 'w' mode overwrites existing files; 'a' appends.

Example: Opening a File

  • customer_file = open('customers.txt', 'r') : Opens the file for read-only access.
  • sales_file = open('sales.txt', 'w') : Opens the file for write access, erasing any existing content. Creates if file does not exist.
  • Warning: Using 'w' overwrites any existing file data.

Specifying the Location of a File

  • If a path isn't included in the filename, the file is assumed to be in the same directory as the program.
  • You can provide a file path for accurate file referencing using the r prefix (e.g., r'C:\Users\...).

Writing Data to a File

  • Use the write method of the file object to write data to the file.
  • Format: file_variable.write(string)

Example: Writing Data to a File

  • customer_file.write('Charles Pace\n')
  • Python programmers usually concatenate a newline character (\n) when writing data to complete a line.

Example: Open File- Writing Data to a File – Close File

  • Python programs can write to files.
  • Show example using file_write.py that writes three lines of text into a new text file.

Reading Data From a File

  • read method reads the entire file into memory. Returns the content as a string.
  • readline method reads one line from the file. Return the entire line, including newline characters (\n).

Line read From a File

  • Show example using line_read.py that reads from a file line by line.

Concatenating a Newline to a String

  • Adding a newline character (\n) to the end of strings before writing to a file, ensures new data adds to the end of a line.

Concatenating a Newline to and Stripping it From a String

  • To format data correctly in files, especially during line-by-line processing, the newline character (\n) should be appropriately handled when writing and reading data from files.

Appending Data to an Existing File

  • Use the 'a' mode to append data to the end of an existing file, instead of overwriting it.
  • Preserves existing file contents.

Writing and Reading Numeric Data

  • Numbers must be converted to strings using the str function to be written to a text file.
  • Reading from a file requires converting strings to numeric types (using int or float) before mathematical operations can be performed.

Using Loops to Process Files

  • Files often hold large amounts of data.
  • Loops are commonly used for reading from and writing to a file, especially when the amount of data is unknown.
  • readline method returns an empty string once it reaches the end of the file.
  • This can be used as a sentinel within a while loop to detect the end of the file.

Using Python's For Loop to Read Lines

  • Python's for loop iterates through each line in a file until the iteration reaches the end of the file, automatically.

Processing Records

  • Records represent data items, each consisting of related fields.
  • Writing records to files: Fields written sequentially, one after another
  • Reading from files: Each field read sequentially until complete.

Fields in A Records & Records in A File

  • Conceptual illustration of the organization of fields and records in a file. Shows example of fields associated with records.

Process Records

  • Processing records from input and writing them to files using structured approach.

Exceptions

  • Exceptions are errors that happen during program execution. They lead to abrupt program termination if not handled.
  • Python uses try...except statements to handle exceptions gracefully.
  • Traceback provides detailed information about errors

Exceptions (IOError)

  • IOError: Occurs when a file cannot be accessed correctly (e.g., file not found), which often interrupts successful file processing.
  • Demonstrates how to handle this issue.

Exceptions (try suite & handler)

  • try...except statements manage errors.
  • The try block contains code that might raise exceptions.
  • The except block handles a specific kind of exception if it occurs.
  • Example code demonstrates how to handle IOError.

Handling Multiple Exceptions

  • A program may encounter several exception types, and a try...except code block must be capable of handling several different types of errors.
  • An except block handles any exception that occurs in the corresponding try block.
  • The order of except blocks is crucial; a broad except block must always be the last one.

Displaying an Exception's Default Error Message

  • Exception handling code can include a try..except..else..finally block to prevent crashes and produce informative messages using a catch-all approach to prevent program termination. Example demonstrates how to print error detail caught.

The else Clause

  • The else clause in try...except statements runs only if no exceptions are raised during the try block execution.

The finally Clause

  • The finally clause in try...except statements ensures a block of code executes regardless of whether an exception is raised or not; helpful for cleanup.

What if an Exception Is Not Handled?

  • If an unhandled exception is encountered, the program typically terminates with an error message specific to exception type and where it originated.
  • The Python documentation contains details on handling exceptions for various functions.

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Starting Out with Python - Chapter 6 - Files and Exceptions PDF

Description

Test your knowledge on file handling concepts in programming with this quiz. Explore questions covering file types, access methods, and best practices for managing files in a program. Perfect for beginners and those looking to refresh their understanding of file operations.

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