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115 lines
3.4 KiB
Markdown
115 lines
3.4 KiB
Markdown
# Day 43 - Programming Language: Python Loops, functions, modules and libraries
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Welcome to the second day of Python, and today we will cover some more concepts:
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- Loops
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- Functions
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- Modules and libraries
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- File I/O
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## Loops (for/while):
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Loops are used to repeatedly run a block of code.
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### for loop
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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:
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``` python
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languages = ['Python', 'Go', 'JavaScript']
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# for loop
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for language in languages:
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print(language)
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```
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Output
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```
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Python
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Go
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JavaScript
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```
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### while loop
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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:
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``` python
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i = 1
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n = 5
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# while loop from i = 1 to 5
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while i <= n:
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print(i)
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i = i + 1
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```
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Output:
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```
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1
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2
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3
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4
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5
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```
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## Functions
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Functions are reusable chunks of code with argument/parameters and return values.
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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.
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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:
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``` python
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# function has two arguments num1 and num2
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def add_numbers(num1, num2):
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sum = num1 + num2
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print('The sum is: ',sum)
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```
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``` python
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# calling the function with arguments to add 5 and 2
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add_numbers(5, 2)
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# Output: The sum is: 9
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```
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## Understanding Modules and Importing Libraries:
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A module is a file in Python that contains definitions and statements. Modules let you arrange your code and reuse it across many apps.
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The Standard Library, a sizable collection of Python modules, offers a wide range of capabilities, such as file I/O, regular expressions, and more.
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Additional libraries can be installed using package managers like pip.
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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:
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``` python
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import math
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print(math.sqrt(16)) # 4.0
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```
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## File I/O
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File I/O is used to read and write data to and from files on disk.
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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().
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To save system resources, you should always close the file after you are done with it.
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An example of reading from a file and printing its content:
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``` python
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f = open("90DaysOfDevOps.txt", "r")
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print(f.read())
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f.close()
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```
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## Exception Handling:
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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.
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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.
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``` python
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try:
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f = open("90DaysOfDevOps.txt")
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try:
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f.write("Python is great")
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except:
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print("Something went wrong when writing to the file")
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```
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## Conclusion
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That is it for today, I will see you tomorrow in [Day 44 | Day 3 of Python!](day44.md).
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