python的csv python的csv库

Python的CSV模块使用详解

Python的csv模块是一个用于处理csv文件的内置模块，csv是逗号分隔值（Comma-Separated Values）的缩写，它是一种常见的数据存储格式，用于存储表格数据，在Python中，我们可以使用csv模块来读取、写入和操作csv文件，本文将详细介绍如何使用Python的csv模块进行csv文件的处理。

读取csv文件

1、使用csv.reader()函数读取csv文件

csv.reader()函数可以接收一个文件对象作为参数，返回一个迭代器，每次迭代返回文件中的一行数据，默认情况下，每行数据中的字段是以逗号分隔的。

示例代码：

import csv
with open('example.csv', 'r', encoding='utf-8') as csvfile:
    reader = csv.reader(csvfile)
    for row in reader:
        print(row)

2、使用csv.DictReader()函数读取csv文件

csv.DictReader()函数可以接收一个文件对象作为参数，返回一个迭代器，每次迭代返回一个字典，字典的键为字段名，值为字段值，这样我们就可以直接通过字段名访问字段值，而不需要知道字段的位置。

示例代码：

import csv
with open('example.csv', 'r', encoding='utf-8') as csvfile:
    reader = csv.DictReader(csvfile)
    for row in reader:
        print(row)

写入csv文件

1、使用csv.writer()函数写入csv文件

csv.writer()函数可以接收一个文件对象和一个可选的分隔符作为参数，返回一个写入器，我们可以使用写入器的writerow()方法写入一行数据，或者使用writerows()方法写入多行数据。

示例代码：

import csv
data = [['Name', 'Age', 'City'], ['Alice', '30', 'New York'], ['Bob', '25', 'Los Angeles']]
with open('output.csv', 'w', encoding='utf-8', newline='') as csvfile:
    writer = csv.writer(csvfile)
    writer.writerows(data)

2、使用csv.DictWriter()函数写入csv文件

csv.DictWriter()函数可以接收一个文件对象和一个可选的分隔符作为参数，返回一个写入器，我们可以使用写入器的writeheader()方法写入表头，然后使用writerow()方法或writerows()方法写入数据，与csv.writer()不同的是，我们需要先创建一个字典列表，字典的键为字段名，值为字段值。

示例代码：

import csv
data = [{'Name': 'Alice', 'Age': '30', 'City': 'New York'}, {'Name': 'Bob', 'Age': '25', 'City': 'Los Angeles'}]
fieldnames = ['Name', 'Age', 'City']
with open('output.csv', 'w', encoding='utf-8', newline='') as csvfile:
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
    writer.writeheader()
    writer.writerows(data)

其他功能

除了基本的读取和写入功能外，Python的csv模块还提供了一些其他功能，如设置字段分隔符、设置引号字符等，这些功能可以通过传递相应的参数给open()函数来实现。

import csv
from io import StringIO
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