Question

我无法弄清楚为什么第104行会返回无效语法，有人可以指出我正确的方向吗？它与我使用elif的方式有关吗？对不起，如果这是一个新手问题！

第104行是printGrammar里面的workingDict.keys（）循环中for项目中的else语句

 import sys
    import string
    from collections import defaultdict

    #default length of 3
    stringLength = 3

    #get last argument of command line(file)
    if len(sys.argv) == 1:
        #get a length from user
        try:
            stringLength = int(input('Length? '))
            filename = input('Filename: ')
        except ValueError:
            print("Not a number")

    elif len(sys.argv) == 2:
        #get a length from user
        try:
            stringLength = int(input('Length? '))
            filename = sys.argv[1]
        except ValueError:
            print("Not a number")

    elif len(sys.argv) == 3:
        filename = sys.argv[2]
        stringLength  = sys.argv[1].split('l')[1]
    else:
        print("Invalid input!")


    #get start symbol
    with open(filename, "r") as grammar:
        #read file 
        lines = grammar.readlines()
        start = lines[0].split('=')[0]
        start = start.replace(" ", "")


    #checks

    #print(stringLength)
    #print(filename)
    #print(start)
    def str2dict(filename):
        result = defaultdict(list)
        with open(filename, "r") as grammar:
            #read file 
            lines = grammar.readlines()
            count = 0

            #loop through
            for line in lines:
                #append info 
                line = line.rstrip()

                result[line[0]].append(line.split('=')[1])

        return result


    workingDict = str2dict("Binary.txt")
    print(workingDict)



    def printGrammar(result):
        sentenceList = []
        workList = []
        workList.append(start)
        i = 0
        firstNT = ""


        #While the worklist is not empty:
        while(len(workList) != 0):
            #Get and delete one potential sentence s from the worklist.
            symbol = workList.pop()
            #If the | s | > N, continue.
            if len(str(symbol).replace(" ", "")) > int(stringLength):
                continue 

            else:
                if str(symbol) in workingDict.keys():
                    #append the right derivation
                    for item in workingDict.get(symbol):
                        workList.append(list(item.replace(" ", "")))
                    #workList.append(str(workingDict.get(symbol)))
                    #add derivation
                    print(workingDict.keys())   
            #If s has no nonterminals, print s and continue.
            for item in workingDict.keys():
                print("test")
                print(''.join(item))
                if len(item) != 1:
                    continue

                #if the element is in dictionary, dont print    
                elif ''.join(item) in workingDict.keys():
                    continue

                print(symbol)
                #if element is not in dictionary, print
                else:
                    print("THIS IS A TERMINAL!!")
                    print(item)
            #Choose the leftmost nonterminal NT.
            print(workList)
            #For all productions NT -> rhs:
                #Replace NT in s with rhs; call it tmp.
                #Store tmp on worklist.






        return workList
    print (printGrammar(workingDict))

Answer 1

你需要缩进

行

print(symbol)

与continue处于同一级别。

Python字典if / else语法无效

1 个答案: