python - 无法弄清楚如何使用表达式在 Python 中验证加拿大邮政编码

Question

我正在尝试制作一个程序，它从用户那里获取邮政编码输入并检查它是否有效。到目前为止，我有:

postalCode = input("Postal code: ")

postalCode = postalCode.replace(" ", "")

postalCode = postalCode.lower()

letters = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]
numbers = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]

valid = True

for i in range(0, len(postalCode), 2):
  if postalCode[i] not in letters or postalCode[i+1] not in numbers:
  valid = False
  break

if(valid):
  print("Valid postal code.")
else:
  print("Not a valid postal code.")

代码运行良好，但我知道使用表达式会更可行，但我一直无法弄清楚它们是如何工作的。

加拿大 zip 格式为:L/N/L N/L/N

谢谢

Answer 1

无正则解决方案:

弄清楚你的事实 - a-z 是错误的，由于相似而省略了一些字母:

A Neufundland               B Nova Scotia           C Prince Edward Island
E New Brunswick             G Québec-Ost            H Montréal und Laval
J Québec-West               K Ontario-Ost           L Ontario-Mitte
M Groß-Toronto              N Ontario-Südwest       P Ontario-Nord
R Manitoba                  S Saskatchewan          T Alberta
V British Columbia          X NW-Territ. Nunavut    Y Yukon

代码:

def CheckCanadianPostalcodes(p, strictCapitalization=False, fixSpace=True):
    '''returns a Tuple of (boolean, string):
    - (True, postalCode) or 
    - (False, error message) 
    By default lower and upper case characters are allowed,  
    a missing middle space will be substituted.'''

    pc = p.strip()                   # copy p, strip whitespaces front/end
    if fixSpace and len(pc) == 6:
        pc = pc[0:3] + " " + pc[3:]    # if allowed / needed insert missing space

    nums = "0123456789"              # allowed numbers
    alph = "ABCEGHJKLMNPRSTVWXYZ"    # allowed characters (WZ handled below)
    mustBeNums = [1,4,6]             # index of number
    mustBeAlph = [0,2,5]             # index of character (WZ handled below)

    illegalCharacters = [x for x in pc 
                         if x not in (nums + alph.lower() + alph + " ")]

    if strictCapitalization:
        illegalCharacters = [x for x in pc
                             if x not in (alph + nums + " ")]

    if illegalCharacters:
        return(False, "Illegal characters detected: " + str(illegalCharacters))

    postalCode = [x.upper() for x in pc]          # copy to uppercase list

    if len(postalCode) != 7:                      # length-validation
        return (False, "Length not 7")

    for idx in range(0,len(postalCode)):          # loop over all indexes
        ch = postalCode[idx]
        if ch in nums and idx not in mustBeNums:  # is is number, check index
            return (False, "Format not 'ADA DAD'")     
        elif ch in alph and idx not in mustBeAlph: # id is character, check index
            return (False, "Format not 'ADA DAD'") # alpha / digit
        elif ch == " " and idx != 3:               # is space in between
            return (False, "Format not 'ADA DAD'")

    if postalCode[0] in "WZ":                      # no W or Z first char
        return (False, "Cant start with W or Z")

    return (True,"".join(postalCode))    # yep - all good

测试:

testCases = [(True,"A9A 9A9"), (True,"a9a 9a9"), (True,"A9A9A9"),
             (True,"a9a9a9"), (False,"w9A 9A9"), (False,"z9a 9a9"), 
             (False,"a9a 9!9")]

for t in testCases:
    pc = CheckCanadianPostalcodes(t[1])    # output differs, see func description
    assert pc[0] == t[0], "Error in assertion: " + str(t) + " became " + str(pc)
    print(t[1], " => ", pc)

pp = input("Postal code: ") 
print(CheckCanadianPostalcodes(pp))    # output differs, see func description  

输出:

A9A 9A9  =>  (True, 'A9A 9A9')
a9a 9a9  =>  (True, 'A9A 9A9')
A9A9A9  =>  (True, 'A9A 9A9')
a9a9a9  =>  (True, 'A9A 9A9')
w9A 9A9  =>  (False, 'Cant start with W or Z')
z9a 9a9  =>  (False, 'Cant start with W or Z')
a9a 9!9  =>  (False, "Illegal characters detected: ['!']")
Postal code: b2c3d4
(False, "Illegal characters detected: ['d']")

此 answer with regex(未接受)提供正确的正则表达式。

Number of possible postal codes (from wikipedia)

Postal codes do not include the letters D, F, I, O, Q or U, and the first position also does not make use of the letters W or Z. [...] As the Canada Post reserves some FSAs for special functions, such as for test or promotional purposes, (e.g. the H0H 0H0 for Santa Claus, see below) as well as for sorting mail bound for destinations outside Canada. [...]

这让您的 ABCEGHJKLMNPRSTVXY 没有 WZ 作为第一个字符。

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编辑:包含 jl-peyret 的更改建议

• 允许缺少空格
• 并在大写/小写都可以的情况下更清楚