About python

Blocks in python

While in most of the langauges blocks are defined using brackets like {}, (), [] but in python blocks are defined using spaces that is the piece of code that has the same spaces from the start of line belong to that contiguous block.

Example:

for(int i=0;i<=20;i++){ //block start  
    console.log(i)
}   //block end

This is javascript example of printing number from one to 20

i=0
while i<=20:    #block start
    print(i)
                #block end

This is python style of the same.

Why are Blocks important?

Blocks are important because variables scoping depends a lot on them. Variable defined inside a block will only be accessible from inside the block only.

Variables

Python Variable Name Rules

• Must begin with a letter (a - z, A - B) or underscore (_)
• Other characters can be letters, numbers or _
• Case Sensitive
• Can be any (reasonable) length
• There are some reserved words which you cannot use as a variable name because Python uses them for other things.

Good Variable Name

• Choose meaningful name instead of short name. roll_no is better than rn.
• Maintain the length of a variable name. Roll_no_of_a-student is too long?
• Be consistent; roll_no or RollNo
• Begin a variable name with an underscore(_) character for a special case.

Since python in not static typed language you do not need to define the type of variables.

Loops

For

i=0
for i < 10:
    print(i)
    i++

While

i=0
while i<10:
    print(i)
    i++

Loop through objects

a = [1,2,3,4,5,6,7]
for i in a:
    print(i)

a=[{"name":"qw"},{"name":"qwe"}]

for i in a:
    print(a["name"])

Functions

def function_add(var1, var2, var3):
    do_some_work
    return var1+var2+var3

Default arguements in functions

def function_default_arg(var1, var2, var3=10):
    return var1+var2+var3

Here if no value is specified for var3 it will be 10 by default so you can call it like below. It also shows us a form of polymorphism which we will see later in this tutorial.