Pandas Series 属性和方法

Pandas Series 属性和方法，前面介绍了Series基本用法，本章介绍 Series 经常使用的属性和方法。

Series 属性或方法

现在创建一个 Series 并演示如何使用上面所有列出的属性操作。

import pandas as pd
import numpy as np

#Create a series with 100 random numbers
s = pd.Series(np.random.randn(4))
print (s)

执行结果如下:

0    0.573942
1    1.596683
2   -1.211234
3   -0.589423
dtype: float64

axes 示例

返回 Series 索引列表

import pandas as pd
import numpy as np

#Create a series with 100 random numbers
s = pd.Series(np.random.randn(4))
print ("The axes are:")
print (s.axes)

执行结果如下:

The axes are:
[RangeIndex(start=0, stop=4, step=1)]

上面的结果是一个从0到5的值列表的紧凑格式，即：[0,1,2,3,4]。

empty 示例

返回布尔值，表示对象是否为空。返回True则表示对象为空。

import pandas as pd
import numpy as np

#Create a series with 100 random numbers
s = pd.Series(np.random.randn(4))
print ("Is the Object empty?")
print (s.empty)

执行结果如下:

Is the Object empty?
False

ndim 示例

返回基础数据的维数。根据定义，一个Series是一个一维数据结构

import pandas as pd
import numpy as np

#Create a series with 4 random numbers
s = pd.Series(np.random.randn(4))
print (s)

print ("The dimensions of the object:")
print (s.ndim)

执行结果如下:

0    0.533809
1   -1.248059
2    1.030966
3    0.594617
dtype: float64
The dimensions of the object:
1

size 示例

返回基础数据中的元素个数。

import pandas as pd
import numpy as np

#Create a series with 4 random numbers
s = pd.Series(np.random.randn(2))
print (s)
print ("The size of the object:")
print (s.size)

执行结果如下:

0    0.456946
1   -0.027225
dtype: float64
The size of the object:
2

values 示例

以ndarray形式返回 Series 中的实际数据值。

import pandas as pd
import numpy as np

#Create a series with 4 random numbers
s = pd.Series(np.random.randn(4))
print (s)

print ("The actual data series is:")
print (s.values)

执行结果如下:

0    0.446583
1    1.045889
2   -2.095649
3   -0.874373
dtype: float64
The actual data series is:
[ 0.44658348  1.04588871 -2.09564915 -0.87437253]

head() 和 tail() 示例

要查看 Series 或 DataFrame 对象的小样本，请使用head()和tail()方法。
head()返回前n行(观察索引值)。默认数量为5，可以传递自定义数值。

import pandas as pd
import numpy as np

#Create a series with 4 random numbers
s = pd.Series(np.random.randn(4))
print ("The original series is:")
print (s)

print ("The first two rows of the data series:")
print (s.head(2))

执行结果如下:

The original series is:
0   -1.540479
1    0.151597
2   -0.114554
3    2.037501
dtype: float64
The first two rows of the data series:
0   -1.540479
1    0.151597
dtype: float64

tail()返回最后n行(观察索引值)。 默认数量为5，可以传递自定义数值。

import pandas as pd
import numpy as np

#Create a series with 4 random numbers
s = pd.Series(np.random.randn(4))
print ("The original series is:")
print (s)

print ("The last two rows of the data series:")
print (s.tail(2))

执行结果如下:

The original series is:
0    0.180139
1   -0.815171
2   -0.343180
3   -1.810884
dtype: float64
The last two rows of the data series:
2   -0.343180
3   -1.810884
dtype: float64