[英]Possible pandas bug?
Just looking at some strange behavior in Python/Pandas.只是看看 Python/Pandas 中的一些奇怪行为。
I know the setup is convoluted, I was doing some... challenges.我知道设置很复杂,我正在做一些……挑战。
def lucas_n(n):
'''Return the fist n lucas numbers modulo 1_000_007'''
my_list = [1,3]
while len(my_list) < n:
my_list.append((my_list[-1]+my_list[-2])%1_000_007)
return my_list
def f(seq):
'''Look up https://projecteuler.net/problem=739'''
df = pd.Series(seq)
for i in range(len(seq)-1):
df = df.iloc[1:].cumsum()
return df.iloc[0]
x = lucas_n(1e4)
f(x)
>>> -8402283173942682253
In short, x
is a sequence of positive integers, and f
applies consecutive .iloc[1:].cumsum()
operations.简而言之,
x
是一个正整数序列, f
应用连续.iloc[1:].cumsum()
操作。
And the output is negative...而output是负数...
Is this a bug?这是一个错误吗? A data type issue?
数据类型问题?
It appears that you have an integer overflow.您似乎有 integer 溢出。 In Python itself integers can have arbitraty precision, but since pandas/numpy by default use C data types, overflow can happen:
在 Python 中,整数本身可以具有任意精度,但由于 pandas/numpy 默认使用 C 数据类型,可能会发生溢出:
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In order to solve the issue you might want to manually cast the data to Python integers:为了解决这个问题,您可能需要手动将数据转换为 Python 整数:
def f(seq):
'''Look up https://projecteuler.net/problem=739'''
df = pd.Series(seq).astype('int') # Casting to Python integer type
for i in range(len(seq)-1):
df = df.iloc[1:].cumsum()
return df.iloc[0]
This solves overflow issue in my testing.这解决了我测试中的溢出问题。
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