python : Manipulating Arguments from a list of objects.

Question

所以我有以下代码。 merge_files() 函数基本上合并两个文件(字符串)并返回一个列表。该列表用于从对象提供参数。

文件1

['2.02', '-3.88', '15.25']
['4.40', '-2.36', '14.97']

文件2

['P1']
['P2']

问题是，当直接向对象提供值时，函数grade_compass() 工作正常。当对象从解析器中提取相同的值时，它似乎没有经过此函数。

完整代码:

    from ast import literal_eval


class Compass:

   #initialize the attributes
    def __init__(self, coordX, coordY, coordZ, Pos):
        self.coordx = coordX
        self.coordy = coordY
        self.coordz = coordZ
        self.coord_pos = Pos



def merge_files(infile1, infile2):
    with open(infile1) as f1, open(infile2) as f2:
        l3 = [] # this is a list for storing all the lines from both files
        f1_lists = (literal_eval(line) for line in f1)
        f2_lists = (literal_eval(line) for line in f2)
        for l1, l2 in zip(f1_lists, f2_lists):
            l3.append(l1 + l2)
        return l3 # Return all the lines from both text files


def check_step_xrange(coordx):
    if coordx > 0.00 and coordx < 7.99:
        return "short"

def check_step_zrange(coordz):
    if coordz > 4.40 and coordz < 20.00:
        return "short"

# Ignore coordy for now
def grade_compass(coordx, coordy, coordz):
    if check_step_xrange(coordx) == "short" and check_step_zrange(coordz) == "short":
        compass_degree = "compass degree is short"
        return compass_degree


def main():
    file1 = "coordinates1.txt"
    file2 = "coordinates2.txt"
    args = merge_files(file1, file2)

    # List of instances
    compasslist = [Compass(args[i][0], args[i][1], args[i][2], args[i][3]) for i in range(len(args))]

    # I just pull the first instance
    print "\nThis is the object from the object list"
    print compasslist[0].coordx + ' ' + compasslist[0].coordy + ' ' + compasslist[0].coordz + ' ' + compasslist[0].coord_pos
    print grade_compass(compasslist[0].coordx, compasslist[0].coordy, compasslist[0].coordz)

    print "\nThis is the object manually given"
    h = Compass(2.02, -3.88, 15.25, 'P1')
    print h.coordx, h.coordy, h.coordz, h.coord_pos
    print grade_compass(h.coordx, h.coordy, h.coordz)
if __name__ == '__main__':
    main()

第一个输出返回 None。当手动给出时，它会起作用。

输出:

This is the object from the object list
2.02 -3.88 15.25 P1
None


This is the object manually given
2.02 -3.88 15.25 P1
compass degree is short

期望的输出:

This is the object from the object list
2.02 -3.88 15.25 P1
compass degree is short


This is the object manually given
2.02 -3.88 15.25 P1
compass degree is short

Answer 1

我猜这是 Python 2.x，而不是 Python 3.x。

在Python 2中，比较运算符总是成功——并且字符串总是大于整数(或 float )。在 Python 3 中，这是一个 TypeError。

>>> 2 > "2"
False
>>> 2 < "2"
True
>>> 2 < "1"
True
>>> 2 < "-500"

所以，基本上，这段代码中的问题是，您永远不会将从文件中读取的字符串转换为 float 。