CODEWITHSUNDEEP
pythonfloating-point
Eman Rabiah
Eman Rabiah

Reputation: 25

It keeps returning TypeError: a float is required

I already read the similar problems in here but nothing works with me .. what's wrong with this python code .. It keeps returning this error message:

TypeError: a float is required

Beta = float( math.atan([(2 - yr)/(1 - xr)]))
print Beta;

Note that: xr = 2 , yr = 2 are predefined before on the previous lines of the code

Upvotes: 0

Views: 1384

Answers (2)

PM 2Ring
PM 2Ring

Reputation: 55469

In standard mathematical notation, square brackets [] can be used like round brackets () for grouping, but they don't work like that in Python (or most other programming languages). In Python, square brackets are used to denote a list. And as Martijn said, the math.atan() function expects a float argument, not a list.

However, it's generally much better to use the math.atan2() function, which accepts two arguments, like this

math.atan2(delta_y, delta_x)

instead of

math.atan(delta_y / delta_x)

The advantage of math.atan2() is that you can do things like math.atan2(delta_y, 0), which would fail with math.atan(). Also, because the Y and X parts are separate, math.atan2() can determine the correct quadrant for the arctangent from the signs of Y and X.

Upvotes: 0

Martijn Pieters
Martijn Pieters

Reputation: 1121366

You are passing in a list:

[(2 - yr)/(1 - xr)]

That's not a float, it is a list with one element. Remove the square brackets:

Beta = float( math.atan((2 - yr) / (1 - xr)))

Demo:

>>> import math
>>> xr, yr = 3, 4
>>> math.atan([(2 - yr)/(1 - xr)])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: a float is required
>>> math.atan((2 - yr)/(1 - xr))
0.7853981633974483

Be careful with using / in Python 2; if yr and xr are integers, you'll get floor divison. See How can I force division to be floating point? Division keeps rounding down to 0 for ways around that.

Upvotes: 6

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