英文:
ValueError when attempting to concatenate Pandas dataframes by reading CSV into multip chunks
问题
I have loaded CSV文件 into a Pandas dataframe with 5 chunks because using chunks is helpful when displaying a large dataset at once. The code you provided is for dividing the dataframe into chunks and displaying the results.
from IPython.display import display
import pandas as pd
path = 'data/diabetes.csv'
df_reader = pd.read_csv(path, chunksize=5)
for index, chunk in enumerate(df_reader):
if index < 5:
print(f'Chunk index: {index}')
display(chunk)
You encountered an issue when trying to concatenate these chunks into a single dataframe called df, resulting in a ValueError: No objects to concatenate error. Here is your code:
# Create an empty list to store the individual DataFrames
df_list = []
for chunk in df_reader:
# Append each chunk to the list if not empty
df_list.append(chunk)
# Concatenate all the DataFrames
df = pd.concat(df_list)
The issue might be due to the fact that you've already iterated through the chunks in the first loop, and when you try to iterate again in the second loop, there are no more chunks left. To resolve this, you should reset the df_reader iterator before the second loop. Here's the modified code:
# Reset the iterator to start from the beginning
df_reader = pd.read_csv(path, chunksize=5)
# Create an empty list to store the individual DataFrames
df_list = []
for chunk in df_reader:
# Append each chunk to the list if not empty
df_list.append(chunk)
# Concatenate all the DataFrames
df = pd.concat(df_list)
This should resolve the ValueError and allow you to concatenate the chunks into a single dataframe.
英文:
I have loaded csv file into pandas dataframe with 5 chunk because chunk is useful while displaying large dataset at once. It prints 5 rows in each iteration. Here is my code of dividing dataframe into chunk and displaying the result.
from IPython.display import display
import pandas as pd
path = 'data/diabetes.csv'
df_reader = pd.read_csv(path, chunksize=5)
for index, chunk in enumerate(df_reader):
if index < 5:
print(f'Chunk index: {index}')
display(chunk)
Below is the output of first two iteration above.
Now from middle, when i need data in single chunk, there is a problem. I tried to store existing data in new dataframe df by concanating into single chunk, but it raise ValueError: No objects to concatenate. Below is my code.
# Create an empty list to store the individual DataFrames
df_list = []
for chunk in df_reader:
# Append each chunk to the list if not empty
df_list.append(chunk)
# Concatenate all the DataFrames
df = pd.concat(df_list)
You can see I have created a new dataframe called df_reader at the beginning, by reading a CSV file in 5 chunks. However, I am currently facing an issue while trying to concatenate these chunks into a single dataframe called df. Whenever I attempt to do so, I receive the error message: ValueError: No objects to concatenate.
Can you help me identify the cause of this error and suggest a solution?
答案1
得分: 1
你可以简单地使用：
df_reader = pd.read_csv(path, chunksize=5)
pd.concat(df_reader)
英文:
you can simply use:
df_reader = pd.read_csv(path, chunksize=5)
pd.concat(df_reader)
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