Python Lesson 2


Lesson # 2

Hi All,

Comments

Comments are very useful and important in any programming language. In python we also use comments to make our code more readable and definable. But remember

‘Code never lies, but comments lies’ –

So, make your comments as per code so it exactly defines why we write a comment and what we need to explain at that time.

Because programmer works with different languages and on different projects. So, write your comment in that way if you read after 1 year you remember or understand what’s the logic behind and it helps you to figure out why I write this section of code etc.

Syntax of comments
è In python # symbol used for comment
è For multiline you can use # symbol or “”” (three times double quotation)
Example
# single line comment
“””
Comment 1
Comment 2
“””
So, between “”” and “”” is comments in python

Variables

As I told in lesson 1 that in python no need to put the data type for variables in python.
Below are few variables

MyString = “Line 1” -> String
MyNumber = 10 -> Integer

But the rules for writing variable names are

è Should start with letter or underscore
è Cannot start with number i.e. 9MyString (this is wrong)
è Variable contains alpha numeric characters and underscores only
è Variables are case sensitive

So, be careful with variable names. My suggestion is always use letter for creating the name of variable and always make meaningful variable names

Datatypes in Python

There are 7 types of datatypes that are built-in and are below:

1.       Text -> str
2.       Numeric -> int, float, complex
3.       Sequence -> list, tuple, range
4.       Mapping -> dict
5.       Set -> set, frozenset
6.       Boolean -> bool
7.       Binary -> bytes, bytearray, memoryview

You can use method type() to know the datatype of variable

Example

MyString = “Line 1”
Print (“MyString have ” + type(MyString) + “ datatype”)

Complex datatype

In Numeric type the complex is little bit different, for complex we need to add ‘j’ at the end of value, so python interpreter understands this is complex numeric datatype.

Example

MyComplexValue = 10j

Casting

Sometimes we need type casting from one datatype to another

Example

MyString = “10”

But we need to add 20 in MyString but MyString is a string so we cannot add the 20
MyCastVariable = int(MyString) -> This will  return 10 as integer

See you in lesson 3 :-)

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