Python 从csv数据制作直方图

我正在尝试用.CSV文件中的数据制作直方图。我把下面的代码放在一起，当我运行它时，我得到一个int“object is not iterable”错误，有什么想法吗

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

file = "...sp histo.csv"
data = pd.read_csv(file)

year_2016 = np.array(data['2016'])
year_2017 = list(np.array(data['2017']))

small_ret = min(min(year_2016),min(year_2017))
large_ret = max(max(year_2016),max(year_2017))
bins = np.arange(small_ret, large_ret, 0.1)

plt.hist(year_2017,bins=bins, range = 20)
plt.show()

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这一行存在一个问题：

plt.hist(year_2017,bins=bins, range = 20)

根据hist的docstring，range必须是元组：

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哪一行导致了错误？给我们一个最小的、可复制的示例数据。这样，很难说你的错误发生在哪里！

range : tuple or None, optional
    The lower and upper range of the bins. Lower and upper outliers
    are ignored. If not provided, `range` is (x.min(), x.max()). Range
    has no effect if `bins` is a sequence.

    If `bins` is a sequence or `range` is specified, autoscaling
    is based on the specified bin range instead of the
    range of x.