Question

我有一个只有一列的表。我想将我编写的函数应用于该系列的其他每一行。但是，当我这样做时，我会得到一个错误！

The table looks like this:        And I want to get this:
names                             names
bank account                      bank account|bank|account
1256864                           1256864
bank share                        bank share|bank|share
42,566                            42,566          
bank currency                     bank currency|bank|currency
Dollar                            Dollar
batch number                      batch number|batch|number
001444                            001444
...                                ...

这是我编写的代码：

import pandas as pd
import re


df = pd.read_table('list_a.tsv')

def sep_rows (text):
    sperated = '|'.join(re.split(r'\s+', text))
    return text+'|'+sperated

# this applies the function to ALL rows!
print(df['names'].apply(sep_rows))
# I tried to choose every other row
a = df.iloc[::2].apply(sep_rows)

print(a) # But I gen an error!

我明白了：

TypeError: expected string or bytes-like object

Answer 1

您的方法（使用re和apply）过于复杂且缓慢。以下表达式使用本地Pandas向量化，效率更高（运行速度快约4倍）。

evens = df['names'].iloc[::2]    
evens[:] = evens + '|' + evens.str.replace('\s+', '|')
#                       names
#0  bank account|bank|account
#1                    1256864
#2      bank share|bank|share
#3                     42,566

Answer 2

按顺序处理文本，然后您的功能应该可以工作：

def sep_rows(text):
    separated = text.str.replace(r"\s+", "|")
    return text + "|" + separated

df.iloc[::2].apply(sep_rows)

             names
0   bank account|bank|account
2   bank share|bank|share
4   bank currency|bank|currency
6   batch number|batch|number

获得结果的另一种方法是list comprehension：

import re
df['new_column'] = ["|".join((text, re.sub(r"\s+", "|", text))) 
                    if num%2 ==0 else text 
                    for num, text in enumerate(df.names)
                   ]

df

   names                  new_column
0   bank account    bank account|bank|account
1   1256864                          1256864
2   bank share      bank share|bank|share
3   42,566                           42,566
4   bank currency   bank currency|bank|currency
5   Dollar                           Dollar
6   batch number    batch number|batch|number
7   001444                           001444

如何在熊猫系列的每隔一行中应用函数？

2 个答案: