如何将Index转换成列表？

Question

我的索引:

Index([u'Newal', u'Saraswati Khera', u'Tohana'], dtype='object')

我必须使用以下格式将此格式转换为列表:

['Newal','SaraswatiKhera','Tohana']

Answer 1

你可以使用tolist或list:

print df.index.tolist()

print list(df.index)

但是,最快的解决方法是转换np.arry的 (感谢EdChum)values tolist

print df.index.values.tolist()

样品:

import pandas as pd

idx = pd.Index([u'Newal', u'Saraswati Khera', u'Tohana'])
print idx
Index([u'Newal', u'Saraswati Khera', u'Tohana'], dtype='object')

print idx.tolist()
[u'Newal', u'Saraswati Khera', u'Tohana']

print list(idx)
[u'Newal', u'Saraswati Khera', u'Tohana']

如果你需要编码UTF-8:

print [x.encode('UTF8') for x in idx.tolist()]
['Newal', 'Saraswati Khera', 'Tohana']

另一种方案:

print [str(x) for x in idx.tolist()]
['Newal', 'Saraswati Khera', 'Tohana']

但如果unicode字符串字符不在ascii范围内,则会失败.

时间:

import pandas as pd
import numpy as np

#random dataframe
np.random.seed(1)
df = pd.DataFrame(np.random.randint(10, size=(3,3)))
df.columns = list('ABC')
df.index = [u'Newal', u'Saraswati Khera', u'Tohana']
print df

print df.index
Index([u'Newal', u'Saraswati Khera', u'Tohana'], dtype='object')

print df.index.tolist()
[u'Newal', u'Saraswati Khera', u'Tohana']

print list(df.index)
[u'Newal', u'Saraswati Khera', u'Tohana']

print df.index.values.tolist()
[u'Newal', u'Saraswati Khera', u'Tohana']


In [90]: %timeit list(df.index)
The slowest run took 37.42 times longer than the fastest. This could mean that an intermediate result is being cached 
100000 loops, best of 3: 2.18 µs per loop

In [91]: %timeit df.index.tolist()
The slowest run took 22.33 times longer than the fastest. This could mean that an intermediate result is being cached 
1000000 loops, best of 3: 1.75 µs per loop

In [92]: %timeit df.index.values.tolist()
The slowest run took 62.72 times longer than the fastest. This could mean that an intermediate result is being cached 
1000000 loops, best of 3: 787 ns per loop