2

我有一个模型，可以在您上传图片时自动调整图像大小并保存原件。

问题是，当我在管理面板中保存图像时，出现此错误

无法将浮点数转换为十进制。首先将浮点数转换为字符串

File "C:\o\mysite\fruit\models.py" in save
 61.         super(Pic, self).save(*args, **kwargs)
 File "C:\Python26\lib\decimal.py" in __new__
  652.                             "First convert the float to a string")

Exception Type: TypeError at /admin/fruit/pic/add/
Exception Value: Cannot convert float to Decimal.  First convert the float to a string

我只是想不通为什么我会收到这个错误

我的模型.py

class Pic(models.Model):
    user = models.ForeignKey(User)
    image = models.ImageField(
        upload_to="image",
        blank=True
        )
    descrip = models.TextField()
    ratio = models.DecimalField(decimal_places=5,max_digits=10,default=0)

    def __unicode__(self):
        return self.descrip

    def original(self):
        width = self.image.width / float(self.ratio)
        height = self.image.height / float(self.ratio)

        result = "<img src='/media/{0}' height='{1}' width='{2}'>".format(
            self.image, height, width)

    return result

    def save(self, *args, **kwargs):       
        pw = self.image.width
        ph = self.image.height
        mw = 200
        mh = 200

        self.ratio = getWH(pw, ph, mw, mh, 'r')

        super(Pic, self).save(*args, **kwargs)

        if (pw > mw) or (ph > mh):
            filename = str(self.image.path)
            imageObj = img.open(filename)

            ratio = 1

            if (pw > mw):
                ratio = mw / float(pw)
                pw = mw
                ph = int(math.floor(float(ph)* ratio))
            if ( ph > mh):
                ratio = ratio * ( mh /float(ph))
                ph = mh
                pw = int(math.floor(float(ph)* ratio))

            width = getWH(pw, ph, mw, mh, 'w')
            height = getWH(pw, ph, mw, mh, 'h')

            imageObj = imageObj.resize((width, height),img.ANTIALIAS)
            imageObj.save(filename)



def getWH(pw, ph, mw, mh, result):
    ratio = 1

    if (pw > mw):
        ratio = mw / float(pw)
        pw = mw
        ph = int(math.floor(float(ph)* ratio))
    if ( ph > mh):
        ratio = ratio * ( mh /float(ph))
        ph = mh
        pw = int(math.floor(float(ph)* ratio))

    if result == 'w':
        return pw
    elif result == 'h':
        return ph
    else:
        return ratio
4

2 回答 2

6

使用 Python 2.7+：

from decimal import Decimal
Decimal.from_float(234.234)

https://docs.python.org/2/library/decimal.html#decimal.Decimal.from_float

于 2014-05-15T20:27:24.040 回答
4

从官方文档9.4.8. 十进制常见问题

问：为什么模块中不包含 float_to_decimal() 例程？

A. 关于混合二进制和十进制浮点是否可取存在一些问题。此外，它的使用需要注意避免与二进制浮点相关的表示问题：

顺便说一句，您可以在给定的链接中找到答案：

def float_to_decimal(f):
    "Convert a floating point number to a Decimal with no loss of information"
    n, d = f.as_integer_ratio()
    numerator, denominator = Decimal(n), Decimal(d)
    ctx = Context(prec=60)
    result = ctx.divide(numerator, denominator)
    while ctx.flags[Inexact]:
        ctx.flags[Inexact] = False
        ctx.prec *= 2
        result = ctx.divide(numerator, denominator)
    return result

而且这个特性已经包含在 python 2.7 中。

于 2013-04-18T11:25:30.060 回答