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Week-4-2

Comparison Operators Overview

  • Comparison Operators: Used to compare values, determining the relationship between them (e.g., equal, greater than, less than).

Comparison of Data Types

  • Allowed Comparisons:

    • Integers can be compared with integers.

    • Strings can be compared with strings.

    • Floating point numbers can be compared with other floating point numbers.

    • Can also compare integers with floating point numbers.

Issues with Floating Point Comparisons

  • Precision Problems:

    • Floating point numbers often have imprecise internal representations in computers.

    • Visual comparison might suggest equality, but tiny differences may exist at the decimal level.

    • Recommendation: Avoid using equality comparisons for floating point numbers; instead, use greater than or less than comparisons.

Common Comparison Mistakes

  • Floating Point with Integers:

    • Example: Comparing 4 + 1 to 5.0 may yield unexpected results due to precision.

    • Equality Comparisons: Should not be relied upon for floating point numbers.

Comparison of Complex Structures

  • Dictionaries:

    • Two dictionaries must have identical keys and values to be considered equal.

  • Tuples:

    • Comparison begins from the first position, proceeding until a difference is found, determining overall comparison truth.

  • Lists:

    • Comparison with different data types (e.g., integers vs. characters) results in an error.

Assignment vs. Comparison

  • Common Error:

    • Using assignment operator = instead of comparison operator == can lead to logical errors in conditions.

IN and NOT IN Operators

  • Membership Testing:

    • IN: Checks if an item is present in a container (like a list or dictionary).

    • NOT IN: Checks if an item is absent from a container.

Example with Lists

  • List of Football Players:

    • Input a player's name, check membership in a defined list, and execute corresponding print statements based on the presence of the name.

Example with Strings

  • Substring Testing:

    • To check if a substring exists within a larger string using IN or NOT IN operators.

Dictionaries and Keys

  • Checking Keys:

    • Membership tests for dictionaries check if a given item is a key, not a value.

Identity Operators

  • IS and IS NOT:

    • IS: Checks if two variables point to the same object in memory.

    • IS NOT: Checks if two variables do not point to the same object.

Operator Precedence

  • Order of Operations:

    • Parentheses () take highest precedence.

    • Followed by Arithmetic Operations, Relational Operators, Logical NOT, AND, and finally OR.

Code Block Indentation

  • Python Indentation:

    • Code blocks are defined by indentation level.

    • Example: Proper indentation ensures which statements execute based on conditions.

Conditional Expressions

  • Syntax Equivalent to If-Else:

    • Conditional expressions can assign values based on conditions in a concise manner, mirroring if-else structures.

Practical Example: Abbreviation Decoder

  • Structure:

    • Employ a series of conditional tests to decode user inputted abbreviations, returning a relevant output or a default message.

Lab Example: Finding the Smallest Integer

  • Specifications:

    • Input three integers and output the smallest one using conditional comparisons to determine the least value.