Learn to design, develop, and execute basic programs in Python.

Zero to Hero in Python for Data Science

This module provides a comprehensive introduction to the tools that help create various programs, such as documents, movies, and games. We'll start with a brief introduction to data science, followed by simple math, real-world problem solving, and precise writing solutions. Next, we'll learn decision-based solutions demonstrated via flowcharts and explained with execution sheets. Finally, we'll learn to translate our solutions into Python programs using variables, conditional statements, loops, strings, lists, and built-in functions. We'll also learn to create our custom functions in Python. After completing this module, we will have acquired the skills to write basic programs in Python.

Understanding Data Science with a focus on Python

# The process of problem solving
The four stages of problem solving are listed below:
1. **Analyze:** Understand the available resources and constraints of a problem.
2. **Plan:** Write the steps that solve the problem in the form of a program. This is the plan of action that will solve the problem.
3. **Implement:** Execute a computer program to obtain the results.
4. **Evaluate:** Match the results of the program with the desired output to determine success.
 



# Simple language
One of the rules for good writing is to not repeat words. To ensure the readers enjoy what we write, we may use words with similar meanings instead of repeating them. For example, we may use any of the following similar but distinct phrases that mean roughly the same thing:
* Display on the screen
* Show on the monitor
* Print on the display unit
* Display
* Show 
* Print
* Output on the screen
* Send to the screen
* Write to the console

However, we don’t want this type of fancy writing with multiple variations in our programs. We should select one simple way of saying something and use it the same way everywhere, even if we use it ten times in a single program.

Let’s say we pick “print” and use it to mean that we want to show something on the screen. We call this an **instruction** in the programming language. Similarly, we use "input" to mean that we want input from the user.  We only use lowercase for these commands. Using a standardized vocabulary will help others understand our programs.

We’ll create a few simple programs using the above-mentioned simple programming language. Keep in mind that all programs are sequential and follow the instructions one by one in a sequence. We’ll also demonstrate the implementation of the programs with the help of the execution sheets.

# Example programs
Let’s look at some example programs, starting simply and adding complexity.

## Print the product
First, let’s create a program to display the product of $5$ and $7$. This program has two steps—finding the product using the multiplication operator `*` and displaying the resultant answer. 
```
prod = 5 * 7
print prod 
```


The program above is expected to display `35`. In this program, `prod` is the name of the variable that holds the result of `5 * 7`. When we use `prod` with the `print` command, the value will be displayed. Therefore, `print prod` will display the value of the `prod`.

> **Note:** Remember that we're not using Python syntax here. The word `print` is just a simple English word. 

## Label the product
Next, let’s create a program to display the product of $5$ and $7$  along with the text label `"product:"` written before the resulting `prod`.
```
prod = 5 * 7
print "product:"
print prod
```
The program above is expected to display `product: 35`. Notice that text written in double quotes will display as text in the output. Therefore, `"product:"` will be displayed before the value of the variable `prod`. This `"product:"` text is called a **label**.

## More variables
Next, let’s create a program that displays the product of two values stored as separate variables.

```
a = 5
b = 7
prod = a * b
print "product:"
print prod
```
The program above is expected to display the product of two numbers stored in separate variables. Here, `a` and `b` are variables with values `5` and `7`, respectively. In the third line, their product is stored in another variable, `prod`. So, the output `product: 35` is displayed.

## Interaction with the user
Now, let’s create a program that displays the sum of two input values.


```
input a
input b
sum = a + b
print "sum:"
print sum
```
This program is expected to display the sum of two numbers input by the user. In the first line, `input` is used to take input from the user and store it in the `a` variable. In the second line, `input` is used to take input from the user and store it in the `b` variable. The output of this program will change according to the input values. If the user enters `5` and `7`, the output `sum: 12` is displayed.

> **Note:** Remember that we're not using Python syntax here. The word `input` is just a simple English word. 

## Prompt the user
Finally, let’s create a program that displays the difference of two values input by the user with prompt messages.


```
print "Please enter the first integer value:"
input a
print "Please enter the second integer value:"
input b
diff = a - b
print "difference:"
print diff
```

The program above is expected to display a prompt asking the user to enter an integer. After receiving the first input from the user, it shows another prompt to the user for the second input. Then, it shows the difference of the two numbers input by the user.

The text displayed before the `input` command is the prompt for the input of the user. The output of this program will change according to the input values. If we use `5` and `7`, the output `difference: -2` is displayed.



Learn to create a simple sequential program and execute it.


Simple Program and Execution Sheet

Learn to create a simple sequential program and execute it.

What is Data Science

Problem Solving with Simple Programs

Decisions and Branching

Python Basics

Repetition with Loops

Strings and Lists

Functions

Complex Programs

Conclusion

Simple Program and Execution Sheet

The process of problem solving

Simple language

Example programs

Print the product