14.2.?roman.py, 第 2 階段 · Dive Into Python

# 14.2.?`roman.py`, 第 2 階段現在你有了 `roman` 模塊的大概框架，到了開始寫代碼以通過測試的時候了。 ## 例?14.3.?`roman2.py` 這個文件可以從 `py/roman/stage2/` 目錄中找到。如果您還沒有下載本書附帶的樣例程序, 可以 [下載本程序和其他樣例程序](http://www.woodpecker.org.cn/diveintopython/download/diveintopython-exampleszh-cn-5.4b.zip "Download example scripts")。 ``` """Convert to and from Roman numerals""" #Define exceptions class RomanError(Exception): pass class OutOfRangeError(RomanError): pass class NotIntegerError(RomanError): pass class InvalidRomanNumeralError(RomanError): pass #Define digit mapping romanNumeralMap = (('M', 1000), ('CM', 900), ('D', 500), ('CD', 400), ('C', 100), ('XC', 90), ('L', 50), ('XL', 40), ('X', 10), ('IX', 9), ('V', 5), ('IV', 4), ('I', 1)) def toRoman(n): """convert integer to Roman numeral""" result = "" for numeral, integer in romanNumeralMap: while n >= integer: result += numeral n -= integer return result def fromRoman(s): """convert Roman numeral to integer""" pass ``` | | | | --- | --- | | \[1\] | `romanNumeralMap` 是一個用來定義三個內容的元組的元組：1\. 代表大部分羅馬數字的字符。注意不只是單字符的羅馬數字，你同樣在這里定義諸如 `CM` (“比一千少一百，即 900”) 的雙字符，這可以讓稍后編寫的 `toRoman` 簡單一些。2\. 羅馬數字的順序。它們是以降序排列的，從`M` 一路到 `I`。3\. 每個羅馬數字所對應的數值。每個內部的元組都是一個 `(_numeral_，_value_)` 數值對。 | | \[2\] | 這里便顯示出你豐富的數據結構帶來的優勢，你不需要什么特定的邏輯處理減法規則。你只需要通過搜尋 `romanNumeralMap` 尋找不大于輸入數值的最大對應整數即可。只要找到，就在結果的結尾把這個整數對應的羅馬字符添加到輸出結果的末尾，從輸入值中減去這個整數，一遍遍這樣繼續下去。 | ## 例?14.4.?`toRoman` 如何工作如果你不明了 `toRoman` 如何工作，在 `while` 循環的結尾添加一個 `print` 語句： ``` while n >= integer: result += numeral n -= integer print 'subtracting', integer, 'from input, adding', numeral, 'to output' ``` ``` >>> import roman2 >>> roman2.toRoman(1424) subtracting 1000 from input, adding M to output subtracting 400 from input, adding CD to output subtracting 10 from input, adding X to output subtracting 10 from input, adding X to output subtracting 4 from input, adding IV to output 'MCDXXIV' ``` 看來 `toRoman` 可以運轉了，至少手工測試可以。但能通過單元測試嗎？啊哈，不，不完全可以。 ## 例?14.5.?以 `romantest2.py` 測試 `roman2.py` 的輸出要記得用 `-v` 命令行選項運行 `romantest2.py` 開啟詳細信息模式。 ``` fromRoman should only accept uppercase input ... FAIL toRoman should always return uppercase ... ok fromRoman should fail with malformed antecedents ... FAIL fromRoman should fail with repeated pairs of numerals ... FAIL fromRoman should fail with too many repeated numerals ... FAIL fromRoman should give known result with known input ... FAIL toRoman should give known result with known input ... ok fromRoman(toRoman(n))==n for all n ... FAIL toRoman should fail with non-integer input ... FAIL toRoman should fail with negative input ... FAIL toRoman should fail with large input ... FAIL toRoman should fail with 0 input ... FAIL ``` | | | | --- | --- | | \[1\] | 事實上，`toRoman` 的返回值總是大寫的，因為 `romanNumeralMap` 定義的羅馬字符都是以大寫字母表示的。因此這個測試已經通過了。 | | \[2\] | 好消息來了：這個版本的 `toRoman` 函數能夠通過[已知值測試](testing_for_success.html#roman.testtoromanknownvalues.example "例?13.2.?testToRomanKnownValues")。記住，這并不能證明完全沒問題，但至少通過測試多種有效輸入考驗了這個函數：包括每個單一字符的羅馬數字，可能的最大輸入 (`3999`)，以及可能的最長的羅馬數字 (對應于 `3888`)。從這點來看，你有理由相信這個函數對于任何有效輸入都不會出問題。 | | \[3\] | 但是，函數還沒辦法處理無效輸入，每個[無效輸入測試](testing_for_failure.html#roman.tobadinput.example "例?13.3.?測試 toRoman 的無效輸入")都失敗了。這很好理解，因為你還沒有對無效輸入進行檢查，測試用例希望捕捉到特定的異常 (通過 `assertRaises`)，而你根本沒有讓這些異常引發。這是你下一階段的工作。 | 下面是單元測試結果的剩余部分，列出了所有失敗的詳細信息，你已經讓它降到了 10 個。 ``` ====================================================================== FAIL: fromRoman should only accept uppercase input ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 156, in testFromRomanCase roman2.fromRoman, numeral.lower()) File "c:\python21\lib\unittest.py", line 266, in failUnlessRaises raise self.failureException, excName AssertionError: InvalidRomanNumeralError ====================================================================== FAIL: fromRoman should fail with malformed antecedents ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 133, in testMalformedAntecedent self.assertRaises(roman2.InvalidRomanNumeralError, roman2.fromRoman, s) File "c:\python21\lib\unittest.py", line 266, in failUnlessRaises raise self.failureException, excName AssertionError: InvalidRomanNumeralError ====================================================================== FAIL: fromRoman should fail with repeated pairs of numerals ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 127, in testRepeatedPairs self.assertRaises(roman2.InvalidRomanNumeralError, roman2.fromRoman, s) File "c:\python21\lib\unittest.py", line 266, in failUnlessRaises raise self.failureException, excName AssertionError: InvalidRomanNumeralError ====================================================================== FAIL: fromRoman should fail with too many repeated numerals ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 122, in testTooManyRepeatedNumerals self.assertRaises(roman2.InvalidRomanNumeralError, roman2.fromRoman, s) File "c:\python21\lib\unittest.py", line 266, in failUnlessRaises raise self.failureException, excName AssertionError: InvalidRomanNumeralError ====================================================================== FAIL: fromRoman should give known result with known input ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 99, in testFromRomanKnownValues self.assertEqual(integer, result) File "c:\python21\lib\unittest.py", line 273, in failUnlessEqual raise self.failureException, (msg or '%s != %s' % (first, second)) AssertionError: 1 != None ====================================================================== FAIL: fromRoman(toRoman(n))==n for all n ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 141, in testSanity self.assertEqual(integer, result) File "c:\python21\lib\unittest.py", line 273, in failUnlessEqual raise self.failureException, (msg or '%s != %s' % (first, second)) AssertionError: 1 != None ====================================================================== FAIL: toRoman should fail with non-integer input ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 116, in testNonInteger self.assertRaises(roman2.NotIntegerError, roman2.toRoman, 0.5) File "c:\python21\lib\unittest.py", line 266, in failUnlessRaises raise self.failureException, excName AssertionError: NotIntegerError ====================================================================== FAIL: toRoman should fail with negative input ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 112, in testNegative self.assertRaises(roman2.OutOfRangeError, roman2.toRoman, -1) File "c:\python21\lib\unittest.py", line 266, in failUnlessRaises raise self.failureException, excName AssertionError: OutOfRangeError ====================================================================== FAIL: toRoman should fail with large input ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 104, in testTooLarge self.assertRaises(roman2.OutOfRangeError, roman2.toRoman, 4000) File "c:\python21\lib\unittest.py", line 266, in failUnlessRaises raise self.failureException, excName AssertionError: OutOfRangeError ====================================================================== FAIL: toRoman should fail with 0 input ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage2\romantest2.py", line 108, in testZero self.assertRaises(roman2.OutOfRangeError, roman2.toRoman, 0) File "c:\python21\lib\unittest.py", line 266, in failUnlessRaises raise self.failureException, excName AssertionError: OutOfRangeError ---------------------------------------------------------------------- Ran 12 tests in 0.320s FAILED (failures=10) ```