How to use the csv module to read and write CSV files in Python 2.x

How to use the csv module to read and write CSV files in Python 2.x

Introduction:
CSV (Comma Separated Values) is a common file format used to store and exchange data . Python's csv module provides an easy way to read and write CSV files. This article will introduce how to use the csv module to read and write CSV files in Python 2.x, and provide corresponding code examples.

1. Reading CSV files
To read CSV files, you first need to import the csv module. Then, read the contents of the CSV file by opening the file and creating a csv.reader object.

Code example:

import csv

# 打开CSV文件
with open('data.csv', 'r') as file:
    # 创建csv.reader对象
    reader = csv.reader(file)

    # 读取文件内容
    for row in reader:
        # 打印每一行数据
        print(row)

In the above code, we use with open('data.csv', 'r') as file to open the CSV file and create A csv.reader object. We can then read the contents of the file line by line by looping over the csv.reader object. The data of each row is returned in the form of a list, and we can process each row accordingly.

2. Write CSV file
To write data into a CSV file, you also need to import the csv module first. Then, write the CSV file by opening the file and creating a csv.writer object.

Code example:

import csv

# 要写入的数据
data = [
    ['Name', 'Age', 'Gender'],
    ['Alice', '20', 'Female'],
    ['Bob', '25', 'Male'],
    ['Charlie', '30', 'Male']
]

# 打开CSV文件
with open('data.csv', 'w') as file:
    # 创建csv.writer对象
    writer = csv.writer(file)

    # 写入数据
    for row in data:
        writer.writerow(row)

In the above code, we first define the data to be written to the CSV file, which is represented here by a list. Then, we open the CSV file using with open('data.csv', 'w') as file and create a csv.writer object. We then iterate through the data and write each row of data to the file using the writer.writerow(row) method.

3. Specify the delimiter
By default, the csv module uses commas as the delimiter. If the CSV file uses other characters as delimiters, this can be set by specifying the delimiter parameter.

Code example:

import csv

# 打开CSV文件，指定分隔符为分号
with open('data.csv', 'r') as file:
    reader = csv.reader(file, delimiter=';')

    for row in reader:
        print(row)

In the above code, we use the delimiter parameter to set the delimiter to a semicolon. This way, when reading a CSV file, csv.reader will use semicolons as the delimiter for each row of data.

Summary:
This article describes how to use the csv module in Python 2.x to read and write CSV files, and provides corresponding code examples. When reading a CSV file, you need to create a csv.reader object and read the contents of the file line by line by iterating over the object. When writing a CSV file, you need to create a csv.writer object and use the writer.writerow(row) method to write each row of data to the file. Additionally, we also covered how to set the delimiter by specifying the delimiter parameter. The above method can help you use Python 2.x to process data in CSV files.

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