如何获得 pandas 数据帧的行数？ [英] how to get row count of pandas dataframe?

问题描述

我正在尝试用Pandas获取数据帧数df，这里是我的代码

I'm trying to get the number of rows of dataframe df with Pandas, and here is my code

方法1：

total_rows = df.count
print total_rows +1

方法2：

total_rows = df['First_columnn_label'].count
print total_rows +1

这两个代码段都给我这个错误：

both the code snippets give me this error:

TypeError：不支持的+：'instancemethod'和'int'的操作数类型

TypeError: unsupported operand type(s) for +: 'instancemethod' and 'int'

我做错了什么？

编辑：根据 @root 提供的a / 15943975/4230591>答案最好的（最快的）检查df的方式长度要调用：

EDIT: According to the answer given by @root the best (the fastest) way to check df length is to call:

len(df.index)

推荐答案

您可以使用 .shape 正确或者只是 len（DataFrame.index），因为有显着的性能差异：

You can use the .shape property or just len(DataFrame.index) as there are notable performance differences:

In [1]: import numpy as np

In [2]: import pandas as pd

In [3]: df = pd.DataFrame(np.arange(9).reshape(3,3))

In [4]: df
Out[4]: 
   0  1  2
0  0  1  2
1  3  4  5
2  6  7  8

In [5]: df.shape
Out[5]: (3, 3)

In [6]: timeit df.shape
1000000 loops, best of 3: 1.17 us per loop

In [7]: timeit df[0].count()
10000 loops, best of 3: 56 us per loop

In [8]: len(df.index)
Out[8]: 3

In [9]: timeit len(df.index)
1000000 loops, best of 3: 381 ns per loop

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编辑：作为@Dan Allen在评论 len（df.index）和 df [0] .count（）不可互换为计数排除 NaN s，

---

As @Dan Allen noted in the comments len(df.index) and df[0].count() are not interchangeable as count excludes NaNs,

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