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Questions and Answers
What is the purpose of a constructor function in a Python class?
What is the purpose of a constructor function in a Python class?
Which of the following is true about immutable objects in Python?
Which of the following is true about immutable objects in Python?
What is the purpose of the find() and rfind() methods in Python strings?
What is the purpose of the find() and rfind() methods in Python strings?
What is the difference between a text file and a binary file in Python?
What is the difference between a text file and a binary file in Python?
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What is the default file mode when opening a file in Python?
What is the default file mode when opening a file in Python?
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What is the purpose of the seek() method in Python file objects?
What is the purpose of the seek() method in Python file objects?
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What is the purpose of format specifiers in Python f-strings?
What is the purpose of format specifiers in Python f-strings?
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What happens when a file is opened in 'a' mode in Python?
What happens when a file is opened in 'a' mode in Python?
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What happens when calling read twice in a row on the same file object in Python?
What happens when calling read twice in a row on the same file object in Python?
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What is the purpose of a constructor function in creating a custom class?
What is the purpose of a constructor function in creating a custom class?
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Which of the following is true about immutable objects in Python?
Which of the following is true about immutable objects in Python?
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What is the purpose of the 'is' keyword in Python?
What is the purpose of the 'is' keyword in Python?
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What is the difference between a text file and a binary file in Python?
What is the difference between a text file and a binary file in Python?
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What is the default file mode when opening a file in Python?
What is the default file mode when opening a file in Python?
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What is the purpose of the seek method in Python?
What is the purpose of the seek method in Python?
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Which of the following is true about f-strings in Python?
Which of the following is true about f-strings in Python?
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What is the purpose of the len() function in Python?
What is the purpose of the len() function in Python?
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What is the difference between find() and rfind() methods in Python?
What is the difference between find() and rfind() methods in Python?
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Study Notes
Introduction to Objects and Classes in Python
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Objects consist of related data (value) and functions that manipulate that data (methods).
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In Python, almost everything is an object, including integers, strings, floats, and booleans.
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Dates are part of the datetime module in Python, and creating a new date object involves using the date() function.
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A class is a template from which objects are instantiated, while an object describes a particular instance of that class.
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Creating a custom class involves defining its attributes and methods, and a constructor function called init is used to initialize its instance variables.
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Instance variables are variables attached to an object instance, and can be accessed and modified using dot notation.
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Methods are functions attached to an object that can accept arguments and modify instance variables.
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Immutable objects, such as integers and strings, cannot have their value changed, and new objects are created to represent the result in computations.
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Mutable objects, such as custom classes, can be changed and will affect all variables that reference that object.
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In Python, variables reference objects stored in memory, and assignment changes which object a variable references.
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Objects with no references become inaccessible and are automatically removed from memory by Python.
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The is keyword can be used to check whether two variables reference the same object.Python Objects and Strings
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Objects combine data and behavior, and can be defined using classes.
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Instantiating multiple objects of the same class will result in different object instances occupying different locations in memory.
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Mutating one object will not affect the other.
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String literals can be expressed using single or double quotes, and escape sequences can be used to include special characters.
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Alternative ways of expressing string literals include using double quotes or triple quotes for multiline strings.
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A string is a sequence of characters that can be indexed and sliced to retrieve specific characters or substrings.
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The length of a string can be obtained using the len() function.
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The find() and rfind() methods can be used to search for substrings within a string.
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Comparing strings is case-sensitive, but case can be ignored by converting all letters to either lowercase or uppercase.
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The replace() method can be used to replace parts of a string with a specified replacement.
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String manipulation can be performed using for loops, conditional statements, and built-in string methods.
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In the next lecture, we will explore how to create and manipulate strings using f-strings and perform file system operations.Python Strings and Files
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Python provides escape sequences to include characters in strings that can't be written in a straightforward way.
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Different ways of writing string literals in Python include single quotes, double quotes, and triple quotes.
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String manipulation can be done using various built-in string methods.
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F-strings are a convenient way of building strings in Python.
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F-strings reduce the need for string concatenation using the + operator and str() function.
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Format specifiers can be added to an f-string to specify how values are formatted.
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Format specifiers can be used to specify the number of decimal places, width, and alignment of values in an f-string.
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A text file is a file that contains human-readable characters and can be edited in a program like Notepad.
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Binary files do not fundamentally represent their data using human-readable characters.
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Opening a file in Python requires the use of the built-in open() function.
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A file object represents a file in Python and provides methods for reading and writing data.
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The read() method of a file object can be used to read the entire content of a file as a string.Working with Files in Python
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Reading large files at once can be slow or may not fit in memory, so reading line-by-line is a better option.
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The readline method allows reading one line at a time and advances the cursor position in the file.
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Each line includes the newline character at the end, which can be removed using string slicing or replacement.
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The seek method can be used to return the cursor position to the beginning of the file for reading the same lines multiple times.
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Python allows using a file object in a for loop, treating it like a sequence of lines.
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Writing to a file requires opening it in a file mode that allows writing, such as 'w', and using the write method.
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Appending text to an existing file can be done using the file mode 'a' instead of 'w', which erases the file contents.
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The os module provides functions for working with file system paths, identifying paths as files or directories, creating directories, listing directory entries, renaming files/directories, and removing files/directories.
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Absolute paths are fully qualified and globally unique, while relative paths are relative to the current directory.
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The default file mode when opening a file is 'r', which allows reading but not writing.
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Including newline characters (\n) is necessary when writing to a file to indicate new lines.
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When using readline, calling read twice in a row on the same file object returns the entire contents of the file as a string and then an empty string.
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Description
Test your knowledge of Python objects, classes, strings, and files with this quiz! See if you can identify key concepts such as mutability and the use of escape sequences in strings, or understand how to work with file objects and file system paths in Python. This quiz is perfect for beginner and intermediate Python programmers looking to solidify their understanding of these fundamental concepts.
