Podcast
Questions and Answers
What is the purpose of opening a file in Python before reading from or writing to it?
What is the purpose of opening a file in Python before reading from or writing to it?
To access the resource and data stored within the file.
Text files store data in the form of characters.
Text files store data in the form of characters.
True (A)
Binary files store entire data in the form of ____, a group of 8 bits each.
Binary files store entire data in the form of ____, a group of 8 bits each.
bytes
What are the steps involved in file handling in Python according to the provided content?
What are the steps involved in file handling in Python according to the provided content?
In Python, 'r' means ____ when opening a file for reading only.
In Python, 'r' means ____ when opening a file for reading only.
Which function is used to read at most n characters from a file in Python?
Which function is used to read at most n characters from a file in Python?
What does 'w' mean when opening a file in Python for writing?
What does 'w' mean when opening a file in Python for writing?
How is a class defined in Python typically described?
How is a class defined in Python typically described?
Structured programming paradigm is based on operations.
Structured programming paradigm is based on operations.
A ______ in Python is a user-defined data structure that binds the data members and methods into a single unit.
A ______ in Python is a user-defined data structure that binds the data members and methods into a single unit.
What is the purpose of the 'try' block in exception handling?
What is the purpose of the 'try' block in exception handling?
Match the following file permissions with their descriptions:
Match the following file permissions with their descriptions:
What is the purpose of class methods in Python?
What is the purpose of class methods in Python?
Describe the characteristics of static methods in Python.
Describe the characteristics of static methods in Python.
What can constructors in Python be used for?
What can constructors in Python be used for?
Python uses the value of 'num' as a default value if the attribute 'self.num' is not defined in a ______ constructor.
Python uses the value of 'num' as a default value if the attribute 'self.num' is not defined in a ______ constructor.
Match the types of inheritance with their descriptions:
Match the types of inheritance with their descriptions:
What is method overloading in Python?
What is method overloading in Python?
Explain the concept of method overriding in Python.
Explain the concept of method overriding in Python.
Method overriding allows a child class to redefine methods from the parent class.
Method overriding allows a child class to redefine methods from the parent class.
Study Notes
File Handling in Python
- File is a named location on disk to store related information, used to permanently store data in a non-volatile memory (e.g., hard disk).
- File handling involves opening, reading, writing, appending, and closing a file.
File Types
- There are two types of files: text files and binary files.
- Text files store data in the form of characters, used to store characters or strings.
- Binary files store entire data in the form of bytes, used to store text, images, audio, and video.
File Permissions
- Read (r): file can be 'looked at' by the program, but not changed.
- Append (a): file can be added to, file is created if it doesn't already exist.
- Write (w): overwrites existing data, starting from the beginning of the file, file is created if it doesn't already exist.
Reading from a File
- The algorithm: connect to and open the file, read the contents into a variable, output the variable, and close the file.
- Read functions: read(n), readline(), readlines()
- read(n): read at most n characters from the file, reads till end of file if it is negative or None.
- readline(): read and return one line from the file, reads in at most n bytes if specified.
- readlines(): read and return a list of lines from the file, reads in at most n bytes/characters if specified.
Writing & Appending to a File
- Write to a file: open the file in write mode (w), use the write() function to write data, and close the file.
- Append to a file: open the file in append mode (a), use the write() function to write data, and close the file.
Lab Exercises
- Lab Exercise 4: write a Python program to read a text file, extract even and odd numbers, and write them to two separate files.
- Lab Exercise 5:
- 5.1: write a method to write multiple lines of text into a text file.
- 5.2: write a method to create two separate text files containing the square of even integers and the cube of odd numbers found in a source text file.
- 5.3: write a Python program to read a binary file, extract the name of the student with the highest GWA, and output the result.
String Manipulation
- A string in Python is created by enclosing characters in quotes (either single quotes or double quotes)
- Indexing: Python uses zero-based indexing, where the first character of a string has an index of 0
- Accessing characters in a string:
s[0]
,s[1]
, etc. - Slicing:
s[3:5]
returns a substring from index 3 to 5 (excluding 5) - String methods:
len(s)
: returns the length of the strings.find("substring")
: returns the index of the first occurrence of the substrings.count("substring")
: returns the number of occurrences of the substrings.startswith("prefix")
: returns True if the string starts with the prefixs.endswith("suffix")
: returns True if the string ends with the suffixs.isdigit()
: returns True if the string consists of digits onlys.isalpha()
: returns True if the string consists of alphabets onlys.isalnum()
: returns True if the string consists of alphanumeric characters onlys.title()
: returns the string with the first character of each word capitalizeds.upper()
: returns the string in uppercases.lower()
: returns the string in lowercases.strip()
: returns the string with leading and trailing whitespace removeds.lstrip()
: returns the string with leading whitespace removeds.rstrip()
: returns the string with trailing whitespace removeds.replace("old", "new")
: returns the string with all occurrences of "old" replaced with "new"
File Handling
- File types:
- Text files: used to store text data
- Binary files: used to store binary data (such as images)
- File operations:
- Reading from a file:
open("file.txt", "r")
- Writing to a file:
open("file.txt", "w")
- Appending to a file:
open("file.txt", "a")
- Reading from a file:
- File modes:
r
: read modew
: write modea
: append mode
- File permissions:
- Read permission: allows reading from the file
- Write permission: allows writing to the file
- Execute permission: allows executing the file
- Reading from a file:
read(n)
: reads at most n characters from the filereadline()
: reads and returns one line from the filereadlines()
: reads and returns a list of lines from the file
- Writing to a file:
write(string)
: writes the string to the filewritelines(list)
: writes the list of strings to the file
Exception Handling
- Types of exceptions:
- Checked exceptions: occur at compile-time (e.g. syntax errors)
- Unchecked exceptions: occur at runtime (e.g. division by zero)
- Handling exceptions:
try
block: contains the code that might raise an exceptionexcept
block: catches and handles the exceptionelse
block: executes if no exception is raisedfinally
block: executes regardless of whether an exception is raised or not
- Example of exception handling:
try:
# code that might raise an exception
except ExceptionType:
# handle the exception
else:
# execute if no exception is raised
finally:
# execute regardless of whether an exception is raised or not
Object-Oriented Programming
- Programming paradigms:
- Structured programming: focuses on procedures and functions
- Object-oriented programming: focuses on objects and classes
- Object-oriented programming concepts:
- Classes: define the structure and behavior of objects
- Objects: instances of classes
- Inheritance: a class can inherit properties and behavior from another class
- Polymorphism: objects of different classes can be treated as if they were of the same class
- Encapsulation: hiding the implementation details of an object from the outside world
- Class attributes:
- Instance variables: attributes that belong to an instance of a class
- Class variables: attributes that belong to a class
- Class methods:
- Instance methods: methods that belong to an instance of a class
- Class methods: methods that belong to a class
- Static methods: methods that can be called without creating an instance of a class
- Constructors:
__init__
: a special method that is called when an object is created- Default constructors: constructors that are called when no arguments are provided
- Parameterized constructors: constructors that take arguments
- Inheritance:
- Single inheritance: a class inherits from one parent class
- Multiple inheritance: a class inherits from multiple parent classes
- Multilevel inheritance: a class inherits from a parent class that itself inherits from another parent class
- Hybrid inheritance: a combination of multiple and multilevel inheritance
- Method overriding: a child class provides a different implementation of a method that is already defined in its parent class
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Description
Quiz on reading, writing, and appending data to files in Python programming. Test your understanding of file handling concepts in Python.