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.