我想你可以找到它作为torch.jit._builtins.math.factorial但pytorch以及numpy和scipy（Factorial in numpy and scipy）使用python的内置math.factorial：

import math

import numpy as np
import scipy as sp
import torch

print(torch.jit._builtins.math.factorial is math.factorial)
print(np.math.factorial is math.factorial)
print(sp.math.factorial is math.factorial)

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但是，相比之下，除了“主流”math.factorial之外，scipy还包含非常“特殊”的阶乘函数scipy.special.factorial。与math模块中的函数不同，它对数组进行操作：

from scipy import special

print(special.factorial is math.factorial)

False

# the all known factorial functions
factorials = (
    math.factorial,
    torch.jit._builtins.math.factorial,
    np.math.factorial,
    sp.math.factorial,
    special.factorial,
)

# Let's run some tests
tnsr = torch.tensor(3)

for fn in factorials:
    try:
        out = fn(tnsr)
    except Exception as err:
        print(fn.__name__, fn.__module__, ':', err)
    else:
        print(fn.__name__, fn.__module__, ':', out)

factorial math : 6
factorial math : 6
factorial math : 6
factorial math : 6
factorial scipy.special._basic : tensor(6., dtype=torch.float64)

tnsr = torch.tensor([1, 2, 3])

for fn in factorials:
    try:
        out = fn(tnsr)
    except Exception as err:
        print(fn.__name__, fn.__module__, ':', err)
    else:
        print(fn.__name__, fn.__module__, ':', out)

factorial math : only integer tensors of a single element can be converted to an index
factorial math : only integer tensors of a single element can be converted to an index
factorial math : only integer tensors of a single element can be converted to an index
factorial math : only integer tensors of a single element can be converted to an index
factorial scipy.special._basic : tensor([1., 2., 6.], dtype=torch.float64)

内置的math模块（docs）提供了一个函数，将给定积分的阶乘作为int返回。

import math

x = math.factorial(5)
print(x)
print(type(x))

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输出

120
<class 'int'>

型

torch.lgamma计算伽马的对数，其等于（x-1）！

import torch

def log_factorial(x):
  return torch.lgamma(x + 1)

def factorial(x):
  return torch.exp(log_factorial(x))

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