如何使用Python将两个CSV文件的数据合并至单个CSV文件

Hey there! Merging two CSVs like yours (with matching column structures) is a common task, and there are a couple of simple, reliable ways to get it done. Let’s walk through them:

Method 1: Using Python’s Pandas Library #

Pandas is the go-to tool for CSV manipulation—it’s clean, flexible, and handles edge cases smoothly.

Step 1: Install Pandas (if you haven’t already) #

Open your terminal or command prompt and run this to install the library:

pip install pandas

Step 2: Write the Merge Script #

Create a Python file (e.g., merge_csvs.py) with this code:

import pandas as pd

# Load both CSV files into DataFrames
csv1 = pd.read_csv("path/to/your/first.csv")
csv2 = pd.read_csv("path/to/your/second.csv")

# Append rows from the second CSV to the first
merged_data = pd.concat([csv1, csv2], ignore_index=True)

# Save the merged result to a new CSV file
merged_data.to_csv("merged_output.csv", index=False)

Key Notes: #

• Replace "path/to/your/first.csv" and "path/to/your/second.csv" with the actual file paths on your system.
• ignore_index=True resets row numbers so you don’t end up with duplicate indices from the original files.
• If your CSVs have mismatched columns, add sort=False to the concat() function to preserve the original column order (Pandas will default to sorting columns alphabetically otherwise). Missing values from unmatched columns will be filled with NaN.

Method 2: Command-Line with csvstack (csvkit) #

If you prefer working in the terminal without writing code, csvstack (part of the csvkit toolkit) is a great option.

Step 1: Install csvkit #

Run this in your terminal to install the toolkit:

pip install csvkit

Step 2: Merge the CSVs #

Navigate to the folder containing your CSV files, then run:

csvstack first.csv second.csv > merged_output.csv

Key Notes: #

• This works seamlessly when both CSVs have identical column names and order (like your samples).
• If columns don’t match, csvstack will fill missing values with NaN for rows from the CSV that lacks that column.
• To use a non-comma delimiter (e.g., tabs), add -d "\t" to the command.

Quick Pre-Merge Checks #

• Confirm both CSVs use the same delimiter (most are comma-separated, but some use tabs or semicolons).
• Remove any extra blank rows at the end of either CSV to avoid adding empty entries to your merged file.

内容的提问来源于stack exchange，提问作者gomathi subramanian