Python Arrays Lecture Notes

Introduction to Arrays

• Presenter: Ivan 20
• Focus: Understanding arrays in Python.

Difference Between Lists, Tuples, and Arrays

• Lists: Can hold mixed data types (integers, floats, strings).
• Tuples: Immutable version of lists, also allows mixed values.
• Arrays: All elements must be of the same type (e.g., all integers or all floats).

Characteristics of Arrays

• No fixed size: Can be dynamically expanded or shrunk.
• Allows operations such as:
  • append(): To add values.
  • index(): To find the index of a particular value.

Using Arrays in Python

1. Importing the Array Module:

   • Use import array to access array functionalities.
   • Alternatively, import array as a for shorthand usage (e.g., a.array()).
   • Specific functions can also be imported using from array import *.

2. Creating an Array:

   • Syntax: array(typecode, [values])
   • Example for integer array:

     import array  
     vals = array('i', [5, 9, 8, 4, 2])  
     

   • Typecodes:
     • i: signed int
     • I: unsigned int
     • f: float
     • d: double float
     • u: Unicode characters

Working with Array Elements

• Accessing Elements:
  • Indexing starts at 0.
  • Example: vals[0] accesses first element.
• Looping Through Arrays:
  • Using for loops:

    for e in vals:  
        print(e)  
    

  • Length of an array can be found using len(), allowing dynamic ranges.

Operations on Arrays

• Common Methods:
  • append(): Adds an element.
  • remove(): Removes an element.
  • reverse(): Reverses elements in-place.
  • buffer_info(): Returns address and size of the array.
• Creating a Copy:
  • Another array can be created with the same values:

    new_vals = array(vals.typecode, [val for val in vals])  
    

• Power Operation:
  • Example: Assign squares of existing values to another array.

Using While Loops with Arrays

• While loops can also iterate through arrays with necessary condition checks and manual index increments.
• Example of while loop for printing:

  i = 0  
  while i < len(new_array):  
      print(new_array[i])  
      i += 1  
  

Conclusion

• Arrays offer a type-restricted alternative to lists in Python.
• They support various operations and are flexible in terms of size.
• Message from Ivan: Feedback and engagement appreciated through comments and likes.

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Additional Notes

• Arrays are most useful in scenarios where all elements need to be of the same data type for consistency and efficiency purposes.