In this post I have covered everything that we need to know to get started coding in Python. It is broken down to super simple chunks of programming concepts. I hope this might help to refresh the basics or help you get started in writing python. So, lets dig into it starting with this meme:
What is Python and why learn it?
Python is a free general purpose programming language, which means that it can be used to build or program anything and everything with the help of correct tools or libraries. Python is easy to understand, fun to use with tons of great resources to get help from, and is a great backed tool for web development, AI, scientific computing, data analysis and much more. Not to mention, it has great career opportunities.
Operators
Airthmetic Operators
Operator
Description
+
adds
-
subtracts
*
multiplies
/
divides left hand number by right hand
%
modulus - divides left hand number by right hand and returns the remainder
Note: % is also used as placeholders. For example: %s
Relational/Comparison operators
Relational operator help us to compare values to get Boolean value(true or false). Every time we use relational operator we get a Boolean value back. Relational operators are 6 altogether >, <, >=,<=, ==, !=
Logical Operators
and operator
or operator
Dictionaries
Dictionaries are another data type which stores values except it has a key - we use {} brackets:
Tuples
Tuples are another data type where data cannot be changed.
If/Else statement and Nested If/Else statement
The concept of nested if/else is spacing or indexing. If one if/else statement is under another it's called nested.
Elif Statements
It comes in between IF and ELSE statement like - if day is Monday, print something, Elif day is Tuesday, print something, else print this.
Loops
Loops are code that are executed again and again until the condition becomes false. Loops makes your code run faster by executing group of statements multiple times rather one after another.
For loops: It uses RANGE function and can also iterate through a set of data like lists and Tuples. e.g. For something IN in RANGE (2,5,2): print (something)
Range function: It prints in range. It has 2 types. (1,5) or (1,7,1).
**Tip - In order to print range in just one line instead line by line use - list function.
While loops: It repeatedly checks for one single condition, if that condition is true the code runs and if that condition is false the code or the while loop ends.
Pass, Break and Continue (BCP)
These are loop control statements. They deviate the loop from its normal sequence.
Break: All it does is terminates the execution and transfers the execution to the next. It will break out of a for or while loop.
Pass: It is a filler code. If you have if/statement and if part done and for else u use the pass code to fill it out .
Continue: It will bypass any code within a code written underneath it and will make sure the loop iterates over once again.
Try and Except
First we TRY to access the data and if any errors occur or something goes wrong then we can directly go to EXCEPT and tell the user that something is wrong.
Comments and escape character :
#
single line comment
"""
for multiple line comments also end with """
/
before a ' and will make it as a comment
Functions:
Python functions are divided into 3 parts i.e. name, parameter and body.
name - In order to write a python function u have to start the function with the keyword called def followed by the name of the function fahr_to_celsius
parameter - now add the parameter that you want to pass through it later. Here we are just giving it a random name called (temp), you can name whatever you want. Make sure to put it in a parenthesis.
body - Now comes the body of the function. It starts with a keyword called return because it has to return or send the value going through whatever logic we created.
In the above function(image above) you can pass any number as the parameter value. The functions are executed like below:
sh fahr_to_celsius(152)
sh fahr_to_celsius(10)
sh fahr_to_celsius(32)
For above executed function the result will be 66.66, -12.221, 0 respectively.
We can either create our own functions or use the built-in functions. It works the same. Most of the functions that we will be using mostly are already built-in python libraries. If we couldn't find any, we can always create one. There are tons of free python libraries for specific projects. We can always use those libraries. Below are some of the important built-in functions that might be useful for our day-to-day programming tasks:
Built in functions
del - is used to delete
len - returns length of array
max - returns maximum value
min - returns minimum value
append - adds objects to list
count - counts, how many times the object is repeated
abs - absolute value makes negative number positive and positive to positive.
bool- it returns true if it's integer and if it's zero or null it returns false.
dir - it's the directory, it will give the list of functions which we can use.
help- it helps us to find out what each function does.
float() - it converts values including decimal values entered in positive number
Int()- it rounds up the decimal numbers in whole numbers.
len()- in strings it returns the how many items are in array and length of characters in string.
max()- it returns the largest number in the list or largest letter going through ascending order.
min()- it returns the opposite of max.
sum()- it adds the numbers
Note: For some functions dealing with arrays or lists - we use [ ] brackets: Arrays and lists can be used in Python to store any data type (real numbers, strings, etc)
Opening and reading txt files in IDLE
open() - open function will acknowledge the file but doesn't open it. Make sure u use the file path with / in between rather than \ . For e.g: C:/Users/ComputerName ...
read() - after open() function it opens and reads the file.
tell() - after we open the same file again it won't open it's because the pointer is at the last. We use tell function to know where the pointer is and it will return the line number.
seek (0,0) - it moves the pointer to the beginning and now we can read.
close() - it closes the txt file.
Copying text files
write() - this lets you write in the file but replaces the previous written words.
Import os - this is an operating system module. We can use it to rename text files.
Input - it let's input the file name. Note: have an extra space to not get error.
