python 學習手札: 8月 2012

with as

要打開文件，我習慣照書本教的

fobj = open(filename, 'r')

怕文件不存在，可能還得再加個捕捉錯誤

try:
    fobj = open(filename, 'r')
except IOError:
    pass

但有了with as 就方便多了，可以

  1 
  2

with open(filename, 'r') as fobj:
    do something

為了讓class 也能使用，需添加二個函數__enter__和 __exit__

class A:
    def __enter__(self):
        print 'in enter'
    def __exit__(self, e_t, e_v, t_b):
        print 'in exit'

with A() as a:
    print 'in with'


in enter
in with
in exit

使用模組contextlib，便不用構造__enter__和 __exit__

>>> from contextlib import contextmanager
>>> from __future__ import with_statement
>>> @contextmanager
... def context():
...     print 'entering the zone'
...     try:
...         yield
...     except Exception, e:
...         print 'with an error %s'%e
...         raise e
...     else:
...         print 'with no error'
...
>>> with context():
...     print '----in context call------'
...
entering the zone
----in context call------
with no error

官方範例

from contextlib import contextmanager

@contextmanager
def tag(name):
    print "<%s>" % name
    yield
    print "</%s>" % name

>>> with tag("h1"):
...    print "foo"
...
<h1>
foo
</h1>

還有一個closing可在抓網頁資料時使用

from contextlib import closing
import urllib

with closing(urllib.urlopen('http://www.python.org')) as page:
    for line in page:
        print line

LIST的妙用

在彼得．狼的獸窩看到一遍文章覺得蠻有趣的！
Java & Python 程式碼疊疊樂之二

內容主要比較 python&java寫輸入一分數判定等級ABCDE那種

這種東西常見的寫法大部分都是:

#!/usr/bin/python 

# -*- coding: utf-8 -*-

# Filename: gradingRobotOne.py



grade = raw_input("請輸入分數： ")      #利用 raw_input 的函式取得鍵盤輸入

score = int(grade)                      #從 raw_input 取得的字串類型 (String) 資料，轉換為 int 的類型

print "====================="

print "您輸入的分數為：", score



gradeLevel = "未判定！"                  #預設成績等級為「未判定！」

#利用判斷式把輸入的成績分等級

if score > 100 or score < 0:

print "分數應該介於 0 到 100 之間！"

elif score <= 100 and score >= 90:

gradeLevel = "A"

elif score <= 89 and score >= 80:

gradeLevel = "B"

elif score <= 79 and score >=70:

gradeLevel = "C"

elif score <= 69 and score >=60:

gradeLevel = "D"

else:

gradeLevel = "F"



print "成績評定為：", gradeLevel        #印出評定結果

那有趣的是，我看最後面有一個回文提供的寫法，蠻有智慧的！

Grade = ["E","D","C","B","A"];
Score = int(raw_input());
print Grade[int((Score-51)/10)];

直接利用LIST的特性，判定成績，讓代碼大為減少！！！

擲骰子遊戲

模擬烤香腸路邊攤擲骰子遊戲
規則:由雙方各擲一次骰子比大小，一次擲四顆，其中二顆需要同點數，計算另二顆相異點數總和，如四顆同點數，則為最大稱為「一色」，三點則為最小。

# -*- coding: UTF-8 -*-
import random

def score_count(point):
    score = 0
    check = len([i for i in set(point)])
    if check == 1:
        score = 19
    elif check == 2:
        if point.count(max(point)) == 2:
            score = max(point) * 2
        else:
            score = 0
    elif check == 3:
        for i in point:
            if point.count(i) == 1:
                score += i
    else:
        score = 0
    return score

def rand_dice(name):
    i = 1
    score = 0
    while not score:
        point = [random.choice(dice) for c in range(4)]
        score = -1
        score = score_count(point)
        print "%s第 %s 次，擲出:" % (name, i), point
        if score == 19:
            print "一色"
        else:
            print score, "點"
        i += 1
    return score

print "***擲骰子遊戲***"
win, lose = 0, 0
dice = [i for i in range(1,7)]

while 1:
    c_score = rand_dice('電腦')
    play = raw_input('請按Enter擲骰子')
    u_score = rand_dice('玩家')
    if c_score > u_score:
        print '你輸了!'
        lose += 1
    elif c_score < u_score:
        print '你贏了!'
        win += 1
    else:
        print '平手！'
    print '目前戰績%s勝%s負' % (win, lose)
    play = raw_input('是否繼續(y/n)?')
    if play in ('n', 'N'):
        print '目前戰績%s勝%s負' % (win, lose)
        print 'Good Bye!'
        break
    else:
        pass

python 學習手札

2012年8月11日星期六

with as

LIST的妙用

擲骰子遊戲

流量統計

2012年8月11日 星期六

with as

LIST的妙用

擲骰子遊戲

2012年8月11日星期六