我有一个熊猫数据框列中的JSON对象,我想拆分并放入其他列。在数据框中,JSON对象看起来像一个包含字典数组的字符串。该数组可以是可变长度的,包括零,或者该列甚至可以为空。我写了一些代码,如下所示,这是我想要的。列名由两个组件构成,第一个是字典中的键,第二个是字典中键值的子字符串。熊猫DataFrame内的JSON对象
此代码工作正常,但在大数据框上运行时速度非常慢。任何人都可以提供更快(也可能更简单)的方式来做到这一点?此外,如果您发现某些不合理/高效/ pythonic的东西,请随时挑选我已完成的工作。我仍然是一个相对的初学者。感谢堆。
# Import libraries
import pandas as pd
from IPython.display import display # Used to display df's nicely in jupyter notebook.
import json
# Set some display options
pd.set_option('max_colwidth',150)
# Create the example dataframe
print("Original df:")
df = pd.DataFrame.from_dict({'ColA': {0: 123, 1: 234, 2: 345, 3: 456, 4: 567},\
'ColB': {0: '[{"key":"keyValue=1","valA":"8","valB":"18"},{"key":"keyValue=2","valA":"9","valB":"19"}]',\
1: '[{"key":"keyValue=2","valA":"28","valB":"38"},{"key":"keyValue=3","valA":"29","valB":"39"}]',\
2: '[{"key":"keyValue=4","valA":"48","valC":"58"}]',\
3: '[]',\
4: None}})
display(df)
# Create a temporary dataframe to append results to, record by record
dfTemp = pd.DataFrame()
# Step through all rows in the dataframe
for i in range(df.shape[0]):
# Check whether record is null, or doesn't contain any real data
if pd.notnull(df.iloc[i,df.columns.get_loc("ColB")]) and len(df.iloc[i,df.columns.get_loc("ColB")]) > 2:
# Convert the json structure into a dataframe, one cell at a time in the relevant column
x = pd.read_json(df.iloc[i,df.columns.get_loc("ColB")])
# The last bit of this string (after the last =) will be used as a key for the column labels
x['key'] = x['key'].apply(lambda x: x.split("=")[-1])
# Set this new key to be the index
y = x.set_index('key')
# Stack the rows up via a multi-level column index
y = y.stack().to_frame().T
# Flatten out the multi-level column index
y.columns = ['{1}_{0}'.format(*c) for c in y.columns]
# Give the single record the same index number as the parent dataframe (for the merge to work)
y.index = [df.index[i]]
# Append this dataframe on sequentially for each row as we go through the loop
dfTemp = dfTemp.append(y)
# Merge the new dataframe back onto the original one as extra columns, with index mataching original dataframe
df = pd.merge(df,dfTemp, how = 'left', left_index = True, right_index = True)
print("Processed df:")
display(df)
只是一件小事。您可以用'for i,col_b in enumerate(df.iloc [:,df.columns.get_loc(“ColB”)]):'替换您的循环,并相应地更改对该条目的引用以提高可读性。 – Nyps
谢谢!这当然会使它更加简洁和可读。 – Michael