Added Day 2 for Python

Author: rishabkumar7

docs/days/day2.md

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+# Day 2 - Python Loops, functions, modules and libraries
+
+Welcome to the second day of Python, and today we will cover some more concepts:
+- Loops
+- Functions
+- Modules and libraries
+- File I/O
+
+## Loops (for/while):
+
+Loops are used to repeatedly run a block of code.
+
+### for loop
+
+Using the `for` loop, a piece of code is executed once for each element of a sequence (such as a list, string, or tuple). Here is an example of a for loop that prints each programming language in a list:
+
+``` python
+languages = ['Python', 'Go', 'JavaScript']
+
+# for loop
+for language in languages:
+    print(language)
+```
+
+Output
+```
+Python
+Go
+JavaScript
+```
+
+### while loop
+
+The `while loop` is used to execute a block of code repeatedly as long as a condition is True. Here's an example of a while loop that prints the numbers from 1 to 5:
+
+``` python
+i = 1
+n = 5
+
+# while loop from i = 1 to 5
+while i <= n:
+    print(i)
+    i = i + 1
+```
+
+Output:
+```
+1
+2
+3
+4
+5
+```
+
+## Functions
+Functions are reusable chunks of code with argument/parameters and return values.
+Using the `def` keyword in Python, you can define a function. In your programme, functions can be used to encapsulate complex logic and can be called several times.
+Functions can also be used to simplify code and make it easier to read. Here is an illustration of a function that adds two numbers:
+
+``` python
+# function has two arguments num1 and num2
+def add_numbers(num1, num2):
+    sum = num1 + num2
+    print('The sum is: ',sum)
+```
+
+``` python
+# calling the function with arguments to add 5 and 2
+add_numbers(5, 2)
+
+# Output: The sum is: 9
+```
+
+## Understanding Modules and Importing Libraries:
+A module is a file in Python that contains definitions and statements. Modules let you arrange your code and reuse it across many apps.
+The Standard Library, a sizable collection of Python modules, offers a wide range of capabilities, such as file I/O, regular expressions, and more.
+Additional libraries can be installed using package managers like pip.
+You must import a module or library using the import statement in order to use it in your programme. Here is an illustration of how to load the math module and calculate a number's square root using the sqrt() function:
+
+``` python
+import math
+
+print(math.sqrt(16)) # 4.0
+```
+
+## File I/O
+File I/O is used to read and write data to and from files on disk.
+The built-in Python function open() can be used to open a file, after which you can read from and write to it using methods like read() and write().
+To save system resources, you should always close the file after you are done with it.
+An example of reading from a file and printing its content:
+
+``` python
+f = open("90DaysOfDevOps.txt", "r")
+print(f.read())
+f.close()
+```
+
+## Exception Handling:
+
+Exceptions are runtime errors that happen when your programme runs into unexpected circumstances, such dividing by zero or attempting to access a list element that doesn't exist.
+Using a try/except block, you can manage exceptions in Python. The try block's code is run, and if an exception arises, the except block's code is run to handle the exception.
+
+``` python
+try:
+  f = open("90DaysOfDevOps.txt")
+  try:
+    f.write("Python is great")
+  except:
+    print("Something went wrong when writing to the file")
+```
+
+## Conclusion
+
+That is it for today, I will see you tomorrow in Day 3 of Python!