python3.9運行py文件報Import Error: can't import name gcd from fractions

報錯：ImportError: cannot import name ‘gcd’ from ‘fractions’
解決方法：python3.9 gdc 函數在math中，修改dag.py。

來自StackOverFlow上的回答：

 

I'm trying to import a function called gcd from a module called fractions with from fractions import gcd. For some reason, PyCharm throws an ImportError:

    from fractions import gcd
ImportError: cannot import name 'gcd' from 'fractions' 

I had this working before, what am I doing wrong?

 

# Answer 1

Your traceback says Python 3.9 and the documentation says gcd is a function in math

Changed in version 3.9: The math.gcd() function is now used to normalize the numerator and denominator. math.gcd() always return a int type. Previously, the GCD type depended on numerator and denominator.

# Answer 2

It's an issue with old networkx versions. Solve this updating networkx:

conda install -c conda-forge networkx=2.5

# Answer 3

fractions.gcd(a, b) has been deprecated in favor of math.gcd(a, b) since Python 3.5 and has been removed in Python 3.9:

Python Version	fractions.gcd(a, b)	math.gcd(a, b)	math.gcd(*integers)
Python 3.0 - 3.4	X
Python 3.5 - 3.8	X	X
Python 3.9+			X

Note that math.gcd can take more than 2 arguments starting from 3.9, and even 0 or 1 argument work.

# Answer 4

if you want always at least the networkx version that works do:

conda install -y networkx">=2.5"

sometimes adding the -c conda-forge is useful...