python入门及进阶学习记 lesson1
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python入门及进阶学习记 lesson1
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Python 教程
Python是一种易于学习又功能强大的编程语言,它提供了高效的高级数据结构,还有简单有效的面向对象编程.
Python优雅的语法和动态类型, 以及解释型语言的本质, 使它成为多数平台上写脚本和快速开发应用的理想语言.
Python解释器及丰富的标准库以源码或机器码的形式提供, 可以到Python官网免费获取适用于各个主要系统平台的版本, 并可自由地分发. 这个网站还包含许多免费第三方Python模块,程序和工具以及附加文档的发布页面或链接.
Python解释器易于扩展, 可以使用C或C++ (或其它可以通过C调用的语言) 扩展新的功能和数据类型. Python也可用于可定制化软件中的扩展程序语言.
这个教程非正式地介绍Python语言和系统的基本概念和功能, 最好在阅读的时候备一个Python解释器进行练习, 不过所有的例子都是相互独立的, suo
有关标准的对象和模块，参阅 Python 标准库。Python 语言参考 提供了更正式的语言参考。想要编写 C 或者 C++ 扩展可以参考 扩展和嵌入 Python 解释器 和 Python/C API 参考手册。也有不少书籍深入讲解Python 。
对python的了解程度
Python是一个简洁和强大的面向对象的编程语言.可以与Perl,Ruby,Scheme,Java比较.
Python的一些特点:
使用优雅的语法格式,让你的Python程序代码更加易读.
是一种易于使用的语言，使您的程序工作起来很简单。这使得Python在不损害可维护性的情况下，成为原型开发和其他特殊编程任务的理想选择。
附带一个大型标准库，支持许多常见的编程任务，如连接到web服务器、使用正则表达式搜索文本、读取和修改文件。
Python的交互模式使测试短代码段变得很容易。还有一个捆绑的开发环境称为IDLE。
通过添加用编译语言(如C或c++)实现的新模块，可以很容易地进行扩展。
也可以嵌入到应用程序中提供可编程接口。
可以在任何地方运行，包括Mac OS X、Windows、Linux和Unix，Android和iOS也有非官方版本。
从两个意义上说，它是自由软件。下载或使用Python，或将其包含在应用程序中，都不需要任何成本。Python还可以自由修改和重新分发，因为虽然该语言是受版权保护的，但它是在开放源码许可下可用的。
Python的一些编程语言特性包括:
可以使用多种基本数据类型:数字(浮点数、复杂的和无限制长度的长整数)、字符串(ASCII和Unicode)、列表和字典。
Python支持使用类和多重继承进行面向对象编程。
代码可以分为模块和包。
该语言支持引发和捕获异常，从而实现更清晰的错误处理。
数据类型是强类型和动态类型。混合不兼容的类型(例如试图添加字符串和数字)会引发异常，因此错误会更快被捕获。
Python包含高级编程特性，如生成器和列表理解。
Python的自动内存管理使您不必在代码中手动分配和释放内存。
查看Python程序示例代码:
请注意，这些示例是用python2编写的，可能需要一些调整才能在python3下运行。
1 line : Output 输出
print \'Hello, world!\'
2 lines : Input 输入, assignment 赋值
name = raw_input(\'What is your name?\\n\')
print \'Hi, %s.\' % name
↑详见2to3
术语对照表
交互式终端中默认的Python提示符. 往往会显示于能以交互方式在解释器里执行的样式代码之前.
交互式终端中输入特殊代码行时默认的Python提示符, 包括: 缩进的代码块, 成对的分隔符之内 (圆括号,方括号, 花括号或三重引号) , 或是指定一个装饰器之后.
2to3
一个将 Python 2.x 代码转换为 Python 3.x 代码的工具,能够处理大部分通过解析源码并遍历解析树可检测到的不兼容问题.
2to3 包含在标准库中, 模块名为 lib2to3; 并提供一个独立入口点 Tools/scripts/2to3 .
2to3 - 自动将 Python 2 代码转为 Python 3 代码
2to3 的使用
2to3 通常会作为脚本和Python解释器一起安装,你可以在Python根目录的Tools/scripts文件夹下找到它.
2to3 的基本调用参数是一个需要转换的文件或目录列表. 对于目录, 会递归地寻找其中的Python源码.
使用命令:
2to3 example.py
这个命令会打印出和源文件的区别, 通过传入-w参数, 2to3 也可以把需要的改写写回到原文件中 (除非传入了 -n 参数, 否则会为原始文件创建一个副本):
2to3 -w example.py
就拿示例代码中的来进行转换测试: https://wiki.python.org/moin/SimplePrograms
一般这个示例代码是Python2中的
name = raw_input(\'What is your name?\\n\')
print \'Hi, %s.\' % name
保存文件后执行2to3命令(需要将2to3的工具放入系统中才能快速使用)
例如 : F:\\python3.7\\Tools\\scripts
执行时添加 -w 参数
2to3 -w inputName.py
会产生一个原件副本,执行后原本名称的已经更改了:
name = input(\'What is your name?\\n\')
print(\'Hi, %s.\' % name)
执行输出:
3 lines : For loop (循环) , built-in enumerate function (内置枚举函数), new style formatting (新样式格式化)
friends = [\'join\',\'pat\',\'gary\',\'michael\']
for i,name in enumerate(friends):
print "iteration {iteration} is {name}".format(iteration=i,name=name)
2to3后:
friends = [\'jack\',\'kyo\',\'ukyo\',\'lucy\']
for i,name in enumerate(friends):
print("iteration {iteration} is {name}".format(iteration=i,name=name))
之后的一直使用Python 3的示例:
4 lines : Fibonacci (斐波那契数列), tuple assignment (元组赋值)
parents, babies = (1,1)
while babies < 100:
print(\'This generation has {0} babies\'.format(babies))
parents, babies = (babies, parents + babies)
5 lines : Functions (方法)
def greet(name):
print(\'Hello\',name)
greet(\'Jack\')
greet(\'Lucy\')
greet(\'alibaba\')
6 lines : Import(导入依赖), regular expressions(正则表达式)
import re
for test_string in [\'555-1212\',\'ILL-EGAL\']:
if re.match(r\'^\\d{3}-\\d{4}$\',test_string):
print(test_string, \'is a valid US local phone number\')
else:
print(test_string, \'rejected\')
7 lines: Dictionaries(字典), generator expressions (生成表达式)
prices = {\'apple\':0.40, \'banana\':0.50}
my_purchase = {
\'apple\':1,
\'banana\':6}
grocery_bill = sum(prices[fruit] * my_purchase[fruit]
for fruit in my_purchase)
print(\'I owe the grocer $%.2f\' % grocery_bill)
8 lines : Command line arguments(命令行参数) , exception handling(异常处理)
# This program adds up integers in the command line
import sys
try:
total = sum(int(arg) for arg in sys.argv[1:])
print(\'sum =\', total)
except ValueError:
print(\'Please supply integer arguments\')
9 lines : Opening files (打开文件)
# indent your Python code to put into an email
import glob
# glob supports Unix style pathname extensions
python_files = glob.glob(\'*.py\')
for file_name in sorted(python_files):
print(\' -------\' + file_name)
with open(file_name) as f:
for line in f:
print(\' \' + line.rstrip())
print()
10 lines : Time(时间), conditionals(条件表达式), from…import( from…import ), for…else( for…else )
from time import localtime
activities = {8: \'Sleeping\',
9: \'Commuting\',
17: \'Working\',
18: \'Commuting\',
20: \'Eating\',
22: \'Resting\'}
time_now = localtime()
hour = time_now.tm_hour
for activity_time in sorted(activities.keys()):
if hour < activity_time:
print(activities[activity_time])
break
else:
print(\'Unknown,AFK or sleeping!\')
11 lines : Triple-quoted strings (三引号字符串), while loop(while循环)
REFRAIN = \'\'\'
%d bottles of beer on the wall,
%d bottles of beer,
take one down, pass it around,
%d bottles of beer on the wall!
\'\'\'
bottles_of_beer = 99
while bottles_of_beer > 1:
print(REFRAIN % (bottles_of_beer, bottles_of_beer,
bottles_of_beer - 1))
bottles_of_beer -= 1
12 lines : Classes (类)
class BankAccount(object):
def __init__(self, initial_balance=0):
self.balance = initial_balance
def deposit(self, amount):
self.balance += amount
def withdraw(self, amount):
self.balance -= amount
def overdrawn(self):
return self.balance < 0
my_account = BankAccount(15)
my_account.withdraw(5)
print my_account.balance
13 lines : Unit testing with unittest (使用unittest模块进行单元测试)
import unittest
def median(pool):
copy = sorted(pool)
size = len(copy)
if size % 2 == 1:
return copy[(size - 1) / 2]
else:
return (copy[size/2 - 1] + copy[size/2]) / 2
class TestMedian(unittest.TestCase):
def testMedian(self):
self.assertEqual(median([2,9,9,7,9,2,4,5,8]),7)
if __name__ == \'__main__\':
unittest.main()
千万不要把py文件的名字命名为模块名
14 lines : Doctest-based testing(基础文档测试)
def median(pool):
\'\'\'Statistical median to demonstrate doctest.
>>> median([2, 9, 9, 7, 9, 2, 4, 5, 8])
7
\'\'\'
copy = sorted(pool)
size = len(copy)
if size % 2 == 1:
return copy[(size - 1) / 2]
else:
return (copy[size/2 - 1] + copy[size/2]) / 2
if __name__ == \'__main__\':
import doctest
doctest.testmod()
15 lines : itertools (迭代器)
from itertools import groupby
lines = \'\'\'
This is the
first paragraph.
This is the second.
\'\'\'.splitlines()
# Use itertools.groupby and bool to return groups of
# consecutive lines that either have content or don\'t.
for has_chars, frags in groupby(lines,bool):
if has_chars:
print(\' \'.join(frags))
# PRINTS:
# This is the first paragraph.
# This is the second.
16 lines : csv module (csv模块), tuple unpacking(元组分解) , cmp() built-in(cmp()内置)
应该从16开始了 https://wiki.python.org/moin/SimplePrograms
调试了下还是报错:希望之后能再次遇到并解决
import csv
# write stocks data as comma-separated values
from filecmp import cmp
writer = csv.writer(open(\'stocks.csv\',\'wb\',buffering=0))
writer.writerows([
(\'YHOO\'.encode(),\'YaHoo! Inc.\'.encode(),27.38,0.33,1.22),
])
# read stocks data, print status messages
stocks = csv.reader(open(\'stocks.csv\',\'rb\'))
status_labels = {-1:\'down\',0:\'unchanged\',1:\'up\'}
for ticker,name,price,change,pct in stocks:
status = status_labels[cmp(float(change),0.0)]
print(\'%s is %s (%s%%)\' % (name,status,pct))
错误日志:
Traceback (most recent call last):
File "E:/pyCharmFiles/csvtest.py", line 8, in <module>
(\'YHOO\'.encode(),\'YaHoo! Inc.\'.encode(),27.38,0.33,1.22),
TypeError: a bytes-like object is required, not \'str\'
18 lines : 8-Queens Problem (recursion) (8皇后递归问题)
BOARD_SIZE = 8
def under_attack(col,queens):
left = right = col
for r, c in reversed(queens):
left, right = left - 1, right + 1
if c in (left, col, right):
return True
return False
def solve(n):
if n == 0:
return [[]]
smaller_solutions = solve(n - 1)
return [solution+[(n,i+1)]
for i in range(BOARD_SIZE)
for solution in smaller_solutions
if not under_attack(i+1,solution)]
for answer in solve(BOARD_SIZE):
print(answer)
8皇后的问题要持续关注下
打印的输出比较有趣:
E:\\pyCharmFiles\\venv\\Scripts\\python.exe E:/pyCharmFiles/SimplePrograms/8Queens.py
[(1, 4), (2, 2), (3, 7), (4, 3), (5, 6), (6, 8), (7, 5), (8, 1)]
[(1, 5), (2, 2), (3, 4), (4, 7), (5, 3), (6, 8), (7, 6), (8, 1)]
[(1, 3), (2, 5), (3, 2), (4, 8), (5, 6), (6, 4), (7, 7), (8, 1)]
[(1, 3), (2, 6), (3, 4), (4, 2), (5, 8), (6, 5), (7, 7), (8, 1)]
[(1, 5), (2, 7), (3, 1), (4, 3), (5, 8), (6, 6), (7, 4), (8, 2)]
[(1, 4), (2, 6), (3, 8), (4, 3), (5, 1), (6, 7), (7, 5), (8, 2)]
[(1, 3), (2, 6), (3, 8), (4, 1), (5, 4), (6, 7), (7, 5), (8, 2)]
[(1, 5), (2, 3), (3, 8), (4, 4), (5, 7), (6, 1), (7, 6), (8, 2)]
[(1, 5), (2, 7), (3, 4), (4, 1), (5, 3), (6, 8), (7, 6), (8, 2)]
[(1, 4), (2, 1), (3, 5), (4, 8), (5, 6), (6, 3), (7, 7), (8, 2)]
[(1, 3), (2, 6), (3, 4), (4, 1), (5, 8), (6, 5), (7, 7), (8, 2)]
[(1, 4), (2, 7), (3, 5), (4, 3), (5, 1), (6, 6), (7, 8), (8, 2)]
[(1, 6), (2, 4), (3, 2), (4, 8), (5, 5), (6, 7), (7, 1), (8, 3)]
[(1, 6), (2, 4), (3, 7), (4, 1), (5, 8), (6, 2), (7, 5), (8, 3)]
[(1, 1), (2, 7), (3, 4), (4, 6), (5, 8), (6, 2), (7, 5), (8, 3)]
[(1, 6), (2, 8), (3, 2), (4, 4), (5, 1), (6, 7), (7, 5), (8, 3)]
[(1, 6), (2, 2), (3, 7), (4, 1), (5, 4), (6, 8), (7, 5), (8, 3)]
[(1, 4), (2, 7), (3, 1), (4, 8), (5, 5), (6, 2), (7, 6), (8, 3)]
[(1, 5), (2, 8), (3, 4), (4, 1), (5, 7), (6, 2), (7, 6), (8, 3)]
[(1, 4), (2, 8), (3, 1), (4, 5), (5, 7), (6, 2), (7, 6), (8, 3)]
[(1, 2), (2, 7), (3, 5), (4, 8), (5, 1), (6, 4), (7, 6), (8, 3)]
[(1, 1), (2, 7), (3, 5), (4, 8), (5, 2), (6, 4), (7, 6), (8, 3)]
[(1, 2), (2, 5), (3, 7), (4, 4), (5, 1), (6, 8), (7, 6), (8, 3)]
[(1, 4), (2, 2), (3, 7), (4, 5), (5, 1), (6, 8), (7, 6), (8, 3)]
[(1, 5), (2, 7), (3, 1), (4, 4), (5, 2), (6, 8), (7, 6), (8, 3)]
[(1, 6), (2, 4), (3, 1), (4, 5), (5, 8), (6, 2), (7, 7), (8, 3)]
[(1, 5), (2, 1), (3, 4), (4, 6), (5, 8), (6, 2), (7, 7), (8, 3)]
[(1, 5), (2, 2), (3, 6), (4, 1), (5, 7), (6, 4), (7, 8), (8, 3)]
[(1, 6), (2, 3), (3, 7), (4, 2), (5, 8), (6, 5), (7, 1), (8, 4)]
[(1, 2), (2, 7), (3, 3), (4, 6), (5, 8), (6, 5), (7, 1), (8, 4)]
[(1, 7), (2, 3), (3, 1), (4, 6), (5, 8), (6, 5), (7, 2), (8, 4)]
[(1, 5), (2, 1), (3, 8), (4, 6), (5, 3), (6, 7), (7, 2), (8, 4)]
[(1, 1), (2, 5), (3, 8), (4, 6), (5, 3), (6, 7), (7, 2), (8, 4)]
[(1, 3), (2, 6), (3, 8), (4, 1), (5, 5), (6, 7), (7, 2), (8, 4)]
[(1, 6), (2, 3), (3, 1), (4, 7), (5, 5), (6, 8), (7, 2), (8, 4)]
[(1, 7), (2, 5), (3, 3), (4, 1), (5, 6), (6, 8), (7, 2), (8, 4)]
[(1, 7), (2, 3), (3, 8), (4, 2), (5, 5), (6, 1), (7, 6), (8, 4)]
[(1, 5), (2, 3), (3, 1), (4, 7), (5, 2), (6, 8), (7, 6), (8, 4)]
[(1, 2), (2, 5), (3, 7), (4, 1), (5, 3), (6, 8), (7, 6), (8, 4)]
[(1, 3), (2, 6), (3, 2), (4, 5), (5, 8), (6, 1), (7, 7), (8, 4)]
[(1, 6), (2, 1), (3, 5), (4, 2), (5, 8), (6, 3), (7, 7), (8, 4)]
[(1, 8), (2, 3), (3, 1), (4, 6), (5, 2), (6, 5), (7, 7), (8, 4)]
[(1, 2), (2, 8), (3, 6), (4, 1), (5, 3), (6, 5), (7, 7), (8, 4)]
[(1, 5), (2, 7), (3, 2), (4, 6), (5, 3), (6, 1), (7, 8), (8, 4)]
[(1, 3), (2, 6), (3, 2), (4, 7), (5, 5), (6, 1), (7, 8), (8, 4)]
[(1, 6), (2, 2), (3, 7), (4, 1), (5, 3), (6, 5), (7, 8), (8, 4)]
[(1, 3), (2, 7), (3, 2), (4, 8), (5, 6), (6, 4), (7, 1), (8, 5)]
[(1, 6), (2, 3), (3, 7), (4, 2), (5, 4), (6, 8), (7, 1), (8, 5)]
[(1, 4), (2, 2), (3, 7), (4, 3), (5, 6), (6, 8), (7, 1), (8, 5)]
[(1, 7), (2, 1), (3, 3), (4, 8), (5, 6), (6, 4), (7, 2), (8, 5)]
[(1, 1), (2, 6), (3, 8), (4, 3), (5, 7), (6, 4), (7, 2), (8, 5)]
[(1, 3), (2, 8), (3, 4), (4, 7), (5, 1), (6, 6), (7, 2), (8, 5)]
[(1, 6), (2, 3), (3, 7), (4, 4), (5, 1), (6, 8), (7, 2), (8, 5)]
[(1, 7), (2, 4), (3, 2), (4, 8), (5, 6), (6, 1), (7, 3), (8, 5)]
[(1, 4), (2, 6), (3, 8), (4, 2), (5, 7), (6, 1), (7, 3), (8, 5)]
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