Question

python的新手，我正在尝试创建一个小函数，用于将给定数量的字符串实例写入文件（例如，作为文字云工具的输入）。我试过用下面的类做这个，但由于某种原因没有收到任何输出，但也没有错误信息。

我想也许我没有正确地将count声明为整数作为输入？但是，不会显示任何错误消息，这会使其有些混乱。

再次，非常新的Python所以任何帮助以及一些解释将非常感谢:)代码如下！

#Prints multiple instances of a string as input for a word cloud tool


class print_list(object):
    wordlist = []
    def __init__(int(count), word, self):
        self.count = count
        self.word = word

    def write_list(self):
        while count > 0:
            wordlist.append(word)
            print word + "\n"
            count = count - 1
            return wordlist

    def write_file(self):
        my_file = open("cloud.txt", "w")
        for word in wordlist:
            my_file.write(word + "\n")
        my_file.close        


Python = print_list(10, "Python")

Answer 1

class PrintList(object):
    def __init__(self,count, word):# self comes first in your init method
        self.count = count
        self.word = word # use self to refer to instance attributes
        self.wordlist=[]  # make wordlist an attribute


    def write_list(self):
        while self.count > 0:
            self.wordlist.append(self.word)
            print self.word + "\n"
            self.count -= 1
        return self.wordlist

    def write_file(self):
        with  open("cloud.txt", "w") as my_file: # using with automatically closes the file
            for word in self.wordlist:
                my_file.write(word + "\n")


pl = PrintList(10, "Python") # create instance of Printlist class
print pl.write_list() 
pl.write_file()# need to call method on instance to write to the file

Python classes

Answer 2

首先，我确实遇到了语法错误......

class print_list(object):
    #int(count) isn't necessary and causes Syntax Error on my python 2.7
    def __init__(self, count, word): 
        self.count = count
        self.word = word
        #I think wordlist will be more useful here, as a class attribute (1)
        self.wordlist = []

    def write_list(self):
        #I copy the self.count to a local variable (2)
        countCopy = self.count
        while count > 0:
            self.wordlist.append(self.word)
            print self.word + "\n"
            countCopy = countCopy - 1

    def write_file(self):
        #nitpick: hardcoding filenames is bad practice, it would be better to pass it as an argument
        my_file = open("cloud.txt", "w")
        #self.wordlist is the list built in the above function
        #so if this function is called first, self.wordlist is an empty list
        for word in self.wordlist:
            my_file.write(word + "\n")
        #you forgot parentheses below
        my_file.close()

#More code here... (3)

说明：

使wordlist成为一个类属性允许您将一次构建列表保留在类中，并且可以通过其他类方法轻松访问它，例如write_file。
由于这一点，self.count从调用__init__的那一刻起保持不变。
简单地对课程进行实例化不会调用我们已经定义的所有方法。这意味着，除tool = print_list(10, "word")之外，您还必须调用每种方法。顺便说一下，＆＃34; Python＆＃34;是一个糟糕的名字...

一般评论：

你似乎对什么应该是一个类属性（例如self.x而不是x）感到困惑，应该是一个局部变量。以及如何使用这些。默认情况下，Python会查找局部变量但不是类属性。如果您要访问类属性，则必须使用self.为其名称添加前缀。否则，您将获得NameError或只是错误的结果。

Answer 3

你有很多语法错误。首先，self需要先行，类型转换不会发生在函数定义中。所以你的__init__应该是

def __init__(self, count, word):
        self.count = int(count)
        self.word = word

其次，所有属性，例如wordlist count和word都需要在方法中以self.wordlist，self.word等方式进行访问。例如，write_file应为

def write_file(self):
    my_file = open("cloud.txt", "w")
    for word in self.wordlist:
        my_file.write(word + "\n")
    my_file.close

write_list应该是

def write_list(self):
    while self.count > 0:
        self.wordlist.append(self.word)
        print self.word + "\n"
        self.count = self.count - 1
    return self.wordlist

（我也没有缩进return语句，所以循环实际执行，但我认为这是复制到stackexchange错误。）

最后，你没有调用任何方法来填充wordlist并编写它。因此，要让您的类实际编写文件，您需要调用write_file方法。对代码进行这些更改后，我们有：

#Prints multiple instances of a string as input for a word cloud tool


class print_list(object):
    wordlist = []
    def __init__(self, count, word):
        self.count = count
        self.word = word

    def write_list(self):
        while self.count > 0:
            self.wordlist.append(self.word)
            print self.word + "\n"
            self.count = self.count - 1
        return self.wordlist

    def write_file(self):
        my_file = open("cloud.txt", "w")
        for word in self.wordlist:
            my_file.write(word + "\n")
        my_file.close()


Python = print_list(10, "Python")
Python.write_list()
Python.write_file()

使用类 - 空输出将字符串写入文件

3 个答案: