Developer(s)Montreal Institute for Learning Algorithms (MILA), University of Montreal
Initial release2007; 16 years ago (2007)
Final release
1.0.5[1] / 27 July 2020; 3 years ago (27 July 2020)
Written inPython, CUDA
PlatformLinux, macOS, Windows
TypeMachine learning library
LicenseThe 3-Clause BSD License Edit this on Wikidata

Theano is a Python library and optimizing compiler for manipulating and evaluating mathematical expressions, especially matrix-valued ones.[2] In Theano, computations are expressed using a NumPy-esque syntax and compiled to run efficiently on either CPU or GPU architectures.


Theano is an open source project[3] primarily developed by the Montreal Institute for Learning Algorithms (MILA) at the Université de Montréal.[4]

The name of the software references the ancient philosopher Theano, long associated with the development of the golden mean.

On 28 September 2017, Pascal Lamblin posted a message from Yoshua Bengio, Head of MILA: major development would cease after the 1.0 release due to competing offerings by strong industrial players.[5] Theano 1.0.0 was then released on 15 November 2017.[6]

On 17 May 2018, Chris Fonnesbeck wrote on behalf of the PyMC development team[7] that the PyMC developers will officially assume control of Theano maintenance once they step down. On 29 January 2021, they started using the name Aesara for their fork of Theano.[8]

On 29 Nov 2022, the PyMC development team[9] that the PyMC developers will fork the Aesara project under the name PyTensor.

Sample code

The following code is the original Theano's example. It defines a computational graph with 2 scalars a and b of type double and an operation between them (addition) and then creates a Python function f that does the actual computation.[10]

import theano
from theano import tensor

# Declare two symbolic floating-point scalars
a = tensor.dscalar()
b = tensor.dscalar()

# Create a simple expression
c = a + b

# Convert the expression into a callable object that takes (a, b)
# values as input and computes a value for c
f = theano.function([a, b], c)

# Bind 1.5 to 'a', 2.5 to 'b', and evaluate 'c'
assert 4.0 == f(1.5, 2.5)

See also


  1. ^ "Release 1.0.5". 27 July 2020. Retrieved 28 July 2020.
  2. ^ Bergstra, J.; O. Breuleux; F. Bastien; P. Lamblin; R. Pascanu; G. Desjardins; J. Turian; D. Warde-Farley; Y. Bengio (30 June 2010). "Theano: A CPU and GPU Math Expression Compiler" (PDF). Proceedings of the Python for Scientific Computing Conference (SciPy) 2010.
  3. ^ "Github Repository". GitHub.
  4. ^ "".
  5. ^ Lamblin, Pascal (28 September 2017). "MILA and the future of Theano". theano-users (Mailing list). Retrieved 28 September 2017.
  6. ^ "Release Notes – Theano 1.0.0 documentation".
  7. ^ Developers, PyMC (1 June 2019). "Theano, TensorFlow and the Future of PyMC". Medium. Retrieved 27 August 2019.
  8. ^ "Theano-2.0.0". GitHub.
  9. ^ Developers, PyMC (20 November 2022). "PyMC forked Aesara to PyTensor". Retrieved 19 July 2023.
  10. ^ "Theano Documentation Release 1.0.0" (PDF). LISA lab, University of Montreal. 21 November 2017. p. 22. Retrieved 31 August 2018.