A very simple thing - I downloaded python 3.8 and installed numpy. Upon making a very basic program that uses a numpy function, I get an error. I captured all the info that I think is relevant for now:
Traceback (most recent call last):
File "C:/Python/numpytest.py", line 6, in <module>
a=sigmoid(2)
File "C:/Python/numpytest.py", line 4, in sigmoid
return 1/(1+exp(-x))
NameError: name 'exp' is not defined
I'm guessing it isn't even importing numpy but no idea why.
Use np.exp(x) to access Numpy's exp() function.
Otherwise, import Numpy as:
from numpy import *
to use exp() without any prefix.
For example,
import numpy as np
def sigmoid(x):
return 1/(1+np.exp(-x))
a=sigmoid(2)
print(a)
You need to call the np class then the exp function
Also, it is better to copy the text rather than take a picture of it.
Related
I have the following code:
import matplotlib.pyplot as plt
plt.cm.set_cmap("Blues")
This gives me an error:
Traceback (most recent call last):
File ".\lorenz_explorer.py", line 12, in <module>
plt.cm.set_cmap("Blues")
AttributeError: module 'matplotlib.cm' has no attribute 'set_cmap'
My matplotlib version is 3.3.1, and the function certainly exists in the documentation for 3.3.1: Link
Then am I doing something wrong or is this a bug? Do I need to import matplotlib.cm separately or something along those lines?
As the documentation link you provide shows, the name of the function is matplotlib.pyplot.set_cmap, not matplotlib.pyplot.cm.set_cmap. So you can call it with plt.set_cmap("Blues").
In other words, the function is not part of the cm library, which is somewhat counter-intuitive.
I have installed numpy but when I import it, it doesn't work.
from numpy import *
arr=array([1,2,3,4])
print(arr)
Result:
C:\Users\YUVRAJ\PycharmProjects\mycode2\venv\Scripts\python.exe C:/Users/YUVRAJ/PycharmProjects/mycode2/numpy.py
Traceback (most recent call last):
File "C:/Users/YUVRAJ/PycharmProjects/mycode2/numpy.py", line 1, in <module>
from numpy import *
File "C:\Users\YUVRAJ\PycharmProjects\mycode2\numpy.py", line 2, in <module>
x=array([1,2,3,4])
NameError: name 'array' is not defined
Process finished with exit code 1
The problem is you named your script as numpy.py, which is a conflict with the module numpy that you need to use. Just rename your script to something else and will be fine.
Instead of using from numpy import *
Try using this:
import numpy
from numpy import array
And then add your code:
arr=array([1,2,3,4])
print(arr)
EDIT: Even though this is the accepted answer, this may not work under all circumstances. If this doesn't work, see adrtam's answer.
I am new to sympy and still naive about python.... I wanted to solve a trigonometric equation, to find its zeroes. (Once I have syntax, then I will use a more complex function.)
I cannot find the right syntax yet. Here is what I tried at the iPython console in Spyder (Python 2.7):
from sympy.solvers import solve
from sympy import Symbol
x = Symbol('x')
solve(sin(x), x)
I got this error:
Traceback (most recent call last):
File "", line 1, in
solve(sin(x), x)
NameError: name 'sin' is not defined
OK, so I need to have the correct reference to the sine function.
According to the sympy documentation, I thought this was in mpath, but this did not work:
from mpmath import *
Traceback (most recent call last):
File "<ipython-input-7-8dcdd12d9679>", line 1, in <module>
from mpmath import *
ImportError: No module named mpmath
How do I load/access mpmath or some other way to get the sine function?
This fixed it:
from sympy import sin
To access mpmath do this
from sympy.mpmath import *
I'm currently writing a python script which plots a numpy matrix containing some data (which I'm not having any difficulty computing). For complicated reasons having to do with how I'm creating that data, I have to go through terminal. I've done problems like this a million times in Spyder using imshow(). So, I thought I'd try to do the same in terminal. Here's my code:
from numpy import *
from matplotlib import *
def make_picture():
f = open("DATA2.txt")
arr = zeros((200, 200))
l = f.readlines()
for i in l:
j = i[:-1]
k = j.split(" ")
arr[int(k[0])][int(k[1])] = float(k[2])
f.close()
imshow(arr)
make_picture()
Suffice it to say, the array stuff works just fine. I've tested it, and it extracts the data perfectly well. So, I've got this 200 by 200 array of numbers floating around my RAM and I'd like to display it. When I run this code in Spyder, I get exactly what I expected. However, when I run this code in Terminal, I get an error message:
Traceback (most recent call last):
File "DATAmine.py", line 15, in <module>
make_picture()
File "DATAmine.py", line 13, in make_picture
imshow(arr)
NameError: global name 'imshow' is not defined
(My program's called DATAmine.py) What's the deal here? Is there something else I should be importing? I know I had to configure my Spyder paths, so I wonder if I don't have access to those paths or something. Any suggestions would be greatly appreciated. Thanks!
P.S. Perhaps I should mention I'm using Ubuntu. Don't know if that's relevant.
To make your life easier you can use
from pylab import *
This will import the full pylab package, which includes matplotlib and numpy.
Cheers
I have Python 3.3.3 and SymPy 0.7.4.1, both in x64 version and installed locally on my computer. I am using PSPad as a configured editor for Python scripting.
When using imports from library sympy in a module which should solve a set of three linear equations:
from sympy import Matrix, solve_linear_system
from sympy.abc import x, y, z
def main():
system = Matrix (((3,2,-1,1) ,(2,-2,4,-2),(-1,0.5,-1,0)))
print(solve_linear_system(system, x, y,z))
if __name__ == "__main__":
main()
The editor PSPad console output returns the following:
traceback (most recent call last): File "C:\Users\GOODLU~1\AppData\Local\Temp\PSpad\securesafety_DISK_5GB\Programmation\linear system solve SYMPY.py", line 1, in <module>
from sympy import Matrix,solve_linear_system File "C:\Users\GOODLU~1\AppData\Local\Temp\PSpad\securesafety_DISK_5GB\Programmation\sympy.py", line 2, in <module>
from sympy import var,Eq,solve ImportError: cannot import name var
Process completed, Exit Code 1.
Execution time: 00:00.134
Actually, I am wondering myself heavily about those issues:
Why, when typing the same thing, without an object def main(), and entered line by line in IDLE, everything is solved correctly, as: {x: 1.00000000000000, y: -2.00000000000000, z: -2.00000000000000}
Why, my PSPad file with object, having the same computation lines, doesn't work and returns errors?
In fact, I would like to use SymPy in normal python code and get computed results in a list or printed in console( .. as in IDLE). Just in order to avoid some annoying line-to-line IDLE manipulations, what should my code file look like?
The problem seems to be that you have created a file named sympy.py, which has the same name as the sympy module.
Hence, in the from sympy import ... statement, your sympy.py is acting as the sympy module.
Try renaming the file to something else, like sympy_programming_test.py and let know if it works.