Python Environment familiarity

Prerequisite: You are ready for the personal PC environment, mine is Ubuntu14.04,python version for 2.7.6 so start the following environment familiarity experiment.

Experiment One: Install Python

sudo apt-get install python

Experiment Two: Enter the interactive Python interpreter and exit

Python

ctrl-d (shortcut key)

Experiment three: Output one line of characters

Python (go to command line interpreter)

Print "hello,world!"

The following experiments are performed by default in the command interpreter

Experiment Four: The interactive command interpreter can be used as a powerful calculator

Addition: + 4 output

Subtraction: 3-2 Output 1

Multiplication: 3*2 Output 6

Division: 3/2 Output 1 2/3 output 0 (here The division result takes only the integer part, there are two ways to do normal division)

Method One: All with real numbers (also called floating point numbers) 1.0/2.0 output 0.5

Method Two: Change the way Division works

From __future__ Import Division

1/2 Output 0.5

1//2 output 0 (in which case the double slash performs an integer division)

Residual: 10%3 Output 1

Power (exponentiation) 2**3 output 8-3**2 output-9

Experiment five: Using variables

X=3

X*2 Output 6

Experiment Six: Get user input

X=input ("x:")

2

Y=input ("Y:")

3

Print X*y

6

Experiment Seven: function use

2**3 Output 8

POW (2,3) output 8

Experiment Eight: module use

In fact, the module can be imagined as an extension to Python to enhance its functionality. You need to import the module using the Import command

Import Math

MATH.SQRT (9) Output 3.0

can also

From math import sqrt

SQRT (9) Output 3.0

The difference between the two look at themselves, should be able to understand

Experiment Ten: Let the script run like a program, not executed in the command interpreter

1. Add in the first line of the document

#!/usr/bin/env python

2. File name ends with a. py

3. Allow scripts to have executable permissions

chmod a+x hello.py (the a+x here is to add executable permissions to everyone)

4. Run the script with the Python command or double-click the script

Python hello.py

Lab 11: String and Escape symbols

It's like print "hello,world!." , a string is printed after print, and the string must be enclosed by double or single quotation marks.

There is no difference between single and double quotes, but sometimes it can come in handy.

For example, to output a string let's go!, in single quotes to express ' Let's go! ' will report a grammatical error, because there are three single quotes, the machine will not be processed, you must use double quotation marks to express "let's go!". Or here with the escape character \ (is the right slash), the escape character, as the name implies, is the original meaning of the character changes, so you can be the letter T after the ' escape, write ' let\ ' s go! '

If the string is long and spans more than one line, you can use three quotation marks instead of normal quotes

Print ""

Fdafdaf.

Fdefwewf

‘‘‘

This way, in fact, can also write,

Print

FDAFDAF \

Fdefwewf

Escaped with escape characters.

Lab 12: Stitching Strings

Way one: A string is written next to another string, and Python automatically merges them, which is a special method that is sometimes especially useful

' Fdafdaf ' 123456 ' output ' fdafdaf123456 '

Way two: Just like the addition operation

' Hello, ' + ' world! ' Output ' hello,world! '

x= ' 123 ' y= ' abc ' XY This output will error, x+y output ' 123abc '

Experiment 13: String representation

STR (), repr (), and ' ' (anti-quote) can convert the value to ask the string.

Like what:

X=42

y= ' abc '

X+y output will be error, two types of data can not be added

STR (x) +y output ' 42abc '

In fact, just said the escape character, but sometimes this character is not very popular

Like what:

print ' hello,\nworld! ' Will output

Hello

world!

What is this for? It is mainly due to the output of \ n as a newline character, in order to avoid this situation can be so, again to escape

print ' hello,\\nworld! ' Output ' hello,\nworld! '

I can do that.

Print R ' hello,\nworld! ' Also output ' hello,\nworld! '

This is called the original string, and it does not treat the backslash as a special character.

There is also a type of Unicode string (or Unicode object), where ordinary strings in Python are stored internally as 8-bit ASCII code, while Unicode objects are stored as 16-bit Unicode characters and can represent more character sets, which means

Print U ' hello,world! '

This article from "ZYZDBK" blog, declined reprint!

Python Environment familiarity