<h5 id="71-introduction">7.1 INTRODUCTION</h5> <ul> <li>The text introduces the concept of modular programming, which involves dividing a program into separate independent blocks of code or sub-problems with different names and specific functionalities.</li> <li>An example is provided of a company that manufactures tents and calculates the selling price based on user requirements such as height, radius, and slant height of the conical part.</li> <li>The program is then divided into different blocks to calculate the area of the canvas used, the cost of the canvas, and the net payable amount by the customer.</li> <li>The benefits of this approach include improved code management, faster program execution, and the ability to reuse code.</li> <li>The text highlights that while computers can quickly run programs, their task is only to execute the code, and they do not need to understand the algorithm.</li> <li>The concept of modular programming is important for writing complex algorithms and managing bulky and difficult-to-manage programs.</li> </ul> <p>======</p> <h5 id="72-functions">7.2 FUNCTIONS</h5> <ul> <li>A function is a named group of instructions that accomplishes a specific task when invoked in programming.</li> <li>Functions can be defined by a programmer as many times as desired and can be called from different places in the program or from inside another function.</li> <li>The required parameters can be passed to the function while calling it, and it returns a value after execution.</li> <li>Program 7-2 demonstrates the use of functions in calculating the payable amount for a tent, with separate functions defined for calculating the area of the cylindrical and conical parts and the final price after tax.</li> <li>The use of functions makes the program more organized, easier to read, and promotes modularity and reusability.</li> </ul> <p>The equations used in the program are:</p> <ul> <li>Area of cylindrical part: area_cyl = 2 * 3.14 * r * h</li> <li>Area of conical part: area_con = 3.14 * r * l</li> <li>Payable amount: net_price = cost + 0.18 * cost (where cost is the total cost before tax)</li> </ul> <p>======</p> <h5 id="721-the-advantages-of-function">7.2.1 The Advantages of Function</h5> <ul> <li>Functions increase readability of code, particularly for longer programs, by organizing the program and making it easier to understand.</li> <li>Functions reduce code length and make debugging easier by avoiding repetition of same code at multiple places in a program.</li> <li>Functions increase reusability as they can be called from another function or another program, allowing for reuse of already defined functions.</li> <li>Functions help divide work among team members, allowing for parallel completion of tasks.</li> <li>An example of this is the use of function con $(l, r)$ for a rectangular tent base and function post_tax_price(cost) for a 18% tax rate.</li> </ul> <p>======</p> <h5 id="73-user-defined-functions">7.3 USER DEFINED FUNCTIONS</h5> <ul> <li>User defined functions are custom functions created in a Python program.</li> <li>They are designed to perform specific tasks as required by the programmer.</li> <li>This is in addition to the standard library functions that Python provides.</li> <li>User defined functions can be called multiple times in a program, enhancing reusability.</li> <li>To create a user defined function, a name is given to a block of code, and this block can then be executed by calling the function name.</li> </ul> <p>======</p> <h5 id="731-creating-user-defined-function">7.3.1 Creating User Defined Function</h5> <ul> <li>A user-defined function in Python starts with “def” and follows a specific syntax.</li> <li>Parameters are optional and enclosed in “[ ]”. A function may or may not have parameters and may or may not return a value.</li> <li>The function header always ends with a colon (:). The function name should be unique and follow the rules for naming identifiers.</li> <li>The statements outside the function indentation are not considered as part of the function.</li> <li>An example is provided of a function “addnum()” that accepts two numbers, calculates their sum, and displays it.</li> </ul> <p>======</p> <h5 id="732-arguments-and-parameters">7.3.2 Arguments and Parameters</h5> <ul> <li>In programming, an argument is a value passed to a function during the function call, while a parameter is a variable in the function header that receives the value of the argument.</li> <li>User-defined functions can receive values at the time of being called, which are passed as arguments and received in corresponding parameters.</li> <li>The id() function can be used to find the identity of the object that the argument and parameter are referring to, and they are bound to have the same identity.</li> <li>Python allows assigning a default value to the parameter, which is a value that is predecided and assigned to the parameter when the function call does not have its corresponding argument.</li> <li>Default parameters must be the trailing parameters in the function header, meaning if any parameter is having a default value, then all the other parameters to its right must also have default values.</li> </ul> <p>======</p> <h5 id="733-functions-returning-value">7.3.3 Functions Returning Value</h5> <ul> <li>A function may or may not return a value when called.</li> <li>The return statement is used to return values from a function.</li> <li>An example of a user-defined function that returns a value is calcPow(), which calculates the value of Base^exponent.</li> <li>The return statement in calcPow() calculates the result and returns it, which can then be used by the calling function.</li> <li>Python functions can be defined in four ways based on arguments and return values: with no arguments and no return value, with no arguments and with return value(s), with argument(s) and no return value, and with argument(s) and return value(s).</li> </ul> <p>======</p> <h5 id="734-flow-of-execution">7.3.4 Flow of Execution</h5> <ul> <li>Flow of execution in Python is the order in which statements in a program are executed, starting from the first statement and continuing top to bottom.</li> <li>When a function is defined, its statements are not executed until the function is called. When a function is called, the control jumps to the function’s definition and executes its statements.</li> <li>A function must be defined before its call within a program. If a function call precedes the function definition, an error is raised.</li> <li>Functions can return multiple values using tuples. This is useful for returning multiple related values at once.</li> <li>Functions can be used to simulate real-world scenarios, such as a traffic light. A user-defined function can accept input, perform calculations or operations, and return a value. This allows for more complex and dynamic programs.</li> </ul> <p>======</p> <h5 id="74-scope-of-a-variable">7.4 SCOPE OF A VARIABLE</h5> <ul> <li>A variable’s scope defines the part of a program where it can be accessed.</li> <li>Global variables are defined outside any function or block and can be accessed in any function defined afterwards.</li> <li>Local variables are defined inside a function or block and can only be accessed within that function or block.</li> <li>Any changes made to a global variable will affect all functions in the program where that variable can be accessed.</li> <li>If a local variable has the same name as a global variable, the local variable hides the global variable within the function. To access the global variable, the keyword ‘global’ must be prefixed to the variable name in the function.</li> </ul> <p>======</p> <h5 id="75-python-standard-library">7.5 PYTHON STANDARD LIBRARY</h5> <ul> <li>Python’s standard library is extensive, providing many built-in functions.</li> <li>These functions can be called in a program as needed, saving time.</li> <li>The library includes various types of functions, such as those for file and directory operations, networking, internet data handling, and more.</li> <li>It also provides modules for working with mathematical functions, dates and times, and data structures.</li> <li>The standard library is a valuable resource that can help programmers save time and effort by providing commonly used functions.</li> </ul> <p>======</p> <h5 id="751-built-in-functions">7.5.1 Built-in functions</h5> <ul> <li>The absolute value of a number, $\operatorname{abs}(x)$, where $x$ can be an integer or floating point number, is its distance from zero.</li> <li>The function $\operatorname{divmod}(x, y)$, where $x$ and $y$ are integers, returns a tuple containing the quotient and remainder.</li> <li>The function $\max(sequence)$ or $\max(x, y, z, \ldots)$, where $x, y, z, \ldots$ may be integers or floating point numbers, returns the largest number in the sequence or the largest of the arguments.</li> <li>The function $\min(sequence)$ or $\min(x, y, z, \ldots)$, where $x, y, z, \ldots$ may be integers or floating point numbers, returns the smallest number in the sequence or the smallest of the arguments.</li> <li>The function $\operatorname{pow}(x, y [, z])$, where $x, y, z$ may be integers or floating point numbers, returns $x^y$. If $z$ is provided, it returns $(x^y) % z$.</li> <li>The function $\operatorname{sum}(x [, num])$, where $x$ is a numeric sequence and $num$ is an optional argument, returns the sum of all the elements in the sequence from left to right. If $num$ is given, it is added to the sum.</li> <li>The function $\operatorname{len}(x)$, where $x$ can be a sequence or a dictionary, returns the count of elements in $x$.</li> </ul> <p>======</p> <h5 id="752-module">7.5.2 Module</h5> <ul> <li> <p>The text provides a summary of various statistical functions in Python.</p> </li> <li> <p>The <code>statistics</code> module contains functions to calculate the mean, median, and mode of a numeric sequence.</p> </li> <li> <p>The mean is the arithmetic mean of a numeric sequence, calculated as the sum of elements divided by the count of elements.</p> </li> <li> <p>The median is the middle value of a numeric sequence, with half the elements below and half above. If the sequence has an odd number of elements, the median is the middle element.</p> </li> <li> <p>The mode is the most repeated value in a sequence.</p> </li> <li> <p>Python’s <code>from</code> statement can be used to access only the required functions from a module, reducing memory usage.</p> </li> </ul> <p>======</p>