过滤掉特定术语 [英] Filtering out specific terms

问题描述

我编写了一个函数，该函数使用导数乘积规则来查找术语的导数:

I have written a function that uses derivative product rule to find derivative of a term:

def find_term_derivative(term):
    x , y = term
    new_term = (y*x, y-1)
    return new_term

def find_derivative(function_terms):
    new_function = []
    for term in function_terms:

        new_term = find_term_derivative(term)
        new_function.append(new_term)

        filtered_terms = filter(zero_filter, new_term)

find_derivative[(4, 3), (-3, 1)]

输出[(12, 2), (-3, 0)]

但是，我想使用过滤器功能删除所有以零开头的项.

However I want to use the filter function to remove any terms which output begin with zero.

例如 输入[(3, 2), (-11, 0)] 当前输出[(6, 1), (0, -1)]

For example Inputs [(3, 2), (-11, 0)] Currently Outputs [(6, 1), (0, -1)]

但是我要过滤&删除第二项，因为它以0开头，将其从字典new_function中删除

However I want to filter & remove the second term because it begins with 0, removing it from the dictionary new_function

我试图定义一个过滤器函数，该函数分析每个元组的第一项并检查其是否为0，如果为0，则将其删除.这是使用过滤功能的方式吗?

I am trying to define a filter function which analyses the first term of each tuple and checks if its 0, and removes it if is. Is this how the filter function is used?

def zero_filter(variable):
    if new_term [0] = 0:
        return False 
    else:
        return True

推荐答案

与其编写一个标记是否应过滤术语的函数，不如以例程列表结尾来进行过滤.

Rather than writing a function that flags if a term should be filtered, just end your routine with a list comprehension that does the filtering.

filtered_list = [v for v in unfiltered_list if v[0]]

您的代码还有其他一些问题，但是由于您没有询问这些问题，因此我将不再赘述.在我向您展示的行中更改变量以使其适合您的例程.

Your code has some other problems, but since you did not ask about them I'll not go into that. Change the variables in the line I showed you to fit into your routine.

如果您需要Python的 filter函数，则可以用这个.

If you need Python's filter function, you could use this.

def find_term_derivative(term):
    x , y = term
    new_term = (y*x, y-1)
    return new_term

def find_derivative(function_terms):
    new_function = []
    for term in function_terms:
        new_term = find_term_derivative(term)
        new_function.append(new_term)
    return list(filter(zero_filter, new_function))

def zero_filter(atuple):
    """Note if the first element of a tuple is non-zero
    or any truthy value."""
    return bool(atuple[0])

print(find_derivative([(4, 3), (-3, 1)]))
print(find_derivative([(3, 2), (-11, 0)]))

您想要的打印输出是

[(12, 2), (-3, 0)]
[(6, 1)]

我使用pythonic方法在过滤器中进行了非零检查:不是像atuple[0] != 0中那样显式检查该值是否为零，我只是使用bool(atuple[0])检查了该值的真实性".这意味着None或[]或{}或()的值也将被过滤掉.这与您的情况无关.

I did the non-zero check in the filter using the pythonic way: rather than check explicitly that the value is not zero, as in atuple[0] != 0, I just checked the "truthiness" of the value with bool(atuple[0]). This means that values of None or [] or {} or () will also be filtered out. This is irrelevant in your case.

顺便说一句，由于您使用过，所以我使用了zero_filter这个名字，但是在我看来，这并不是最好的名字.也许filter_out_zeros会更好.

By the way, I used the name zero_filter since you did, but that does not seem to me to be the best name. Perhaps filter_out_zeros would be better.

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