csv — CSV (逗号分隔值) 文件读写

源代码： Lib/csv.py

The so-called CSV (Comma Separated Values) format is the most common import and export format for spreadsheets and databases. CSV format was used for many years prior to attempts to describe the format in a standardized way in RFC 4180 . The lack of a well-defined standard means that subtle differences often exist in the data produced and consumed by different applications. These differences can make it annoying to process CSV files from multiple sources. Still, while the delimiters and quoting characters vary, the overall format is similar enough that it is possible to write a single module which can efficiently manipulate such data, hiding the details of reading and writing the data from the programmer.

The csv module implements classes to read and write tabular data in CSV format. It allows programmers to say, “write this data in the format preferred by Excel,” or “read data from this file which was generated by Excel,” without knowing the precise details of the CSV format used by Excel. Programmers can also describe the CSV formats understood by other applications or define their own special-purpose CSV formats.

The csv 模块的 reader and writer objects read and write sequences. Programmers can also read and write data in dictionary form using the DictReader and DictWriter 类。

另请参阅

PEP 305 - CSV (逗号分隔值) 文件 API

The Python Enhancement Proposal which proposed this addition to Python.

模块内容

The csv 模块定义了下列函数：

csv. reader ( csvfile , dialect = 'excel' , ** fmtparams )

返回 reader object that will process lines from the given csvfile . A csvfile must be an iterable of strings, each in the reader’s defined csv format. A csvfile is most commonly a file-like object or list. If csvfile is a file object, it should be opened with newline='' . [ 1 ] An optional dialect parameter can be given which is used to define a set of parameters specific to a particular CSV dialect. It may be an instance of a subclass of the Dialect class or one of the strings returned by the list_dialects() function. The other optional fmtparams keyword arguments can be given to override individual formatting parameters in the current dialect. For full details about the dialect and formatting parameters, see section 方言和格式化参数 .

Each row read from the csv file is returned as a list of strings. No automatic data type conversion is performed unless the QUOTE_NONNUMERIC format option is specified (in which case unquoted fields are transformed into floats).

A short usage example: 

>>> import csv
>>> with open('eggs.csv', newline='') as csvfile:
...     spamreader = csv.reader(csvfile, delimiter=' ', quotechar='|')
...     for row in spamreader:
...         print(', '.join(row))
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