Python day1

[FenWangNZ]

What you need to learn python:

• problem solving skills and abstract thinking
• mechanistic thingking
• good style of coding

Python has:

• technical advantages

• open source--free

• general purpose: data analysis and web programming(Django)

• high-level: it employs syntax a lot closer to human logic

• practical application(应用领域广): finance, economics...

Python basics

linux 命令

• ls---list
• cd---change directory
• mkdir---make directory
• touch---create file
• clear----clear shell
• python---run python script
• exit----exit terminal

Syntax

Indentation: block of code

Commnets:

Data Types:

In Programming, data types is an important concept

Variables can store data of different types, and different types can do different things

Python has the following data types built-in by default, in these categories:

• Text Type: str
• Numeric Types: int, float, complex
• Sequence Types: list, tuple, range
• Mapping Types: set, frozenset
• Boolean Type: bool
• Binary Types: Bytes, bytearray, memoryview

Data Variables:

• Variable 可以看成一个container
• string: str---可以看成一个text
• numeric:
• int---number
• Numbers: There are three numeric types in Python:
• Int, or integer, is a whole number, positive or negative, without decimals, of unlimited length
• Float: Float, or floating point number is a number, positive or negative, containing one or more decimals
• Complex: Complex numbers are written with a jas the imaginary part
• Type Conversion: You can convert from one type to another with the int(), float()and complex() methods
• Random Number: Python does not have a random()function to make a random number, bu Python has a built-in module called random that can be used to make random numbers

Casting:

• Specify a Variable Type
• There may be times when you want to specify a type on to a variable. This can be done with casting. Python is an object-orientated language, and as such it uses classes to define data types, including its primitive types.
• Casting in Python is there done using constructor functions
• int()-Constructs an integer number. From an integer literal, a float literal(by rounding down to the previous whole number), or a string literal( providing the string represents a whole number)
• float()-Constructs a float number from an integer float literal or a string literal( providing the string represents a float or an integer)
• str()- Constructs a string from a wide variety of data types, including strings, integer literals and float literals.

Boolean:

• Boolean Values In Programming you often need to know if an expression is True or False.
• You can evaluate any expression in Python, and get one of two answers, True or False.
• When you compare two values, the expression is evaluated, and Python returns the Boolean answer.
• The only way you get False is there is no value in the context.

Operators:

Operators are used to perform operations on variables values Python divides the operators in the following groups

• Arithmetic Operator

• Assignment Operator

• Comparison Operators

• Identity Operator

• Membership Operators

• Bitwise Operators