14. 文件格式

14.1. csv

csv是逗号分割的文件，使用比较广泛。

14.1.1. csv.writer(csvfile, dialect=’excel’, **fmtparams)

In [59]: import csv

In [60]: with open("eggs.csv",'w',newline='') as f:
    ...:     fw=csv.writer(f,delimiter=' ',quotechar='!',quoting=csv.QUOTE_MINIMAL)
    ...:     fw.writerow([1,2,3,4])
    ...:     fw.writerow([2,3,4,5])
    ...:

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

In [61]: import csv

In [62]: with open('eggs.csv',newline='') as f:
    ...:     fr=csv.reader(f,delimiter=' ',quotechar='|')
    ...:     for row in fr:
    ...:         print(','.join(row))
    ...:
1,2,3,4
2,3,4,5

14.1.3. csv.DictWriter(f, fieldnames, restval=’’, extrasaction=’raise’, dialect=’excel’, *args, **kwds)

In [63]: import csv
    ...:
    ...: with open('names.csv', 'w', newline='') as csvfile:
    ...:     fieldnames = ['first_name', 'last_name']
    ...:     writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
    ...:
    ...:     writer.writeheader()
    ...:     writer.writerow({'first_name': 'Baked', 'last_name': 'Beans'})
    ...:     writer.writerow({'first_name': 'Lovely', 'last_name': 'Spam'})
    ...:     writer.writerow({'first_name': 'Wonderful', 'last_name': 'Spam'})

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

In [64]: import csv

In [65]: with open('names.csv', newline='') as csvfile:
    ...:     reader = csv.DictReader(csvfile)
    ...:     for row in reader:
    ...:         print(row['first_name'], row['last_name'])
    ...:
Baked Beans
Lovely Spam
Wonderful Spam

14.2. configparser

提供ini风跟配置文件的解析，window下的大量配置文件都是使用的ini风格， 还有linux下的yum仓库或者mysql数据库配置文件等等。

ini风格的样例：

[DEFAULT]
ServerAliveInterval = 45
Compression = yes
CompressionLevel = 9
ForwardX11 = yes

[bitbucket.org]
User = hg

[topsecret.server.com]
Port = 50022
ForwardX11 = no

怎么生成上面的配置文件呢？

In [66]: import configparser

In [67]: import configparser
    ...: config = configparser.ConfigParser()
    ...: config['DEFAULT'] = {'ServerAliveInterval': '45',
    ...:                      'Compression': 'yes',
    ...:                      'CompressionLevel': '9'}
    ...: config['bitbucket.org'] = {}
    ...: config['bitbucket.org']['User'] = 'hg'
    ...: config['topsecret.server.com'] = {}
    ...: topsecret = config['topsecret.server.com']
    ...: topsecret['Port'] = '50022'     # mutates the parser
    ...: topsecret['ForwardX11'] = 'no'  # same here
    ...: config['DEFAULT']['ForwardX11'] = 'yes'
    ...: with open('example.ini', 'w') as configfile:
    ...:     config.write(configfile)

上面的代码就可以生成ini的配置文件了，下面是读取解析

In [68]: import configparser

In [69]: config = configparser.ConfigParser()

In [70]: config.sections() Out[70]: []

# 读取配置文件 In [71]: config.read(‘example.ini’) Out[71]: [‘example.ini’]

In [72]: config.sections() Out[72]: [‘bitbucket.org’, ‘topsecret.server.com’]

In [73]: ‘bitbucket.org’ in config Out[73]: True

In [75]: config[‘DEFAULT’][‘Compression’] Out[75]: ‘yes’

In [76]: config.getboolean(‘DEFAULT’,’Compression’) Out[76]: True

# 指定默认值 In [77]: topsecret.getboolean(‘BatchMode’, fallback=True) Out[77]: True

比较通用的一个样例：

import configparser

config = configparser.RawConfigParser()

# Please note that using RawConfigParser's set functions, you can assign
# non-string values to keys internally, but will receive an error when
# attempting to write to a file or when you get it in non-raw mode. Setting
# values using the mapping protocol or ConfigParser's set() does not allow
# such assignments to take place.
config.add_section('Section1')
config.set('Section1', 'an_int', '15')
config.set('Section1', 'a_bool', 'true')
config.set('Section1', 'a_float', '3.1415')
config.set('Section1', 'baz', 'fun')
config.set('Section1', 'bar', 'Python')
config.set('Section1', 'foo', '%(bar)s is %(baz)s!')

# Writing our configuration file to 'example.cfg'
with open('example.cfg', 'w') as configfile:
    config.write(configfile)

14.3. netrc

提供netrc文件的解析能力

14.4. xdrlib

支持外部数据表示标准,提供encode和decode xdr数据。

样例：

import xdrlib
p = xdrlib.Packer()
try:
    p.pack_double(8.01)
except xdrlib.ConversionError as instance:
    print('packing the double failed:', instance.msg)

14.5. plistlib

用于读写主要由Mac OS X使用的“属性列表”文件，并支持二进制文件和XML plist文件。

主要的方法是dumps,dump,load,loads,writePlist,readPlist方法。

pl = dict(
    aString = "Doodah",
    aList = ["A", "B", 12, 32.1, [1, 2, 3]],
    aFloat = 0.1,
    anInt = 728,
    aDict = dict(
        anotherString = "<hello & hi there!>",
        aThirdString = "M\xe4ssig, Ma\xdf",
        aTrueValue = True,
        aFalseValue = False,
    ),
    someData = b"<binary gunk>",
    someMoreData = b"<lots of binary gunk>" * 10,
    aDate = datetime.datetime.fromtimestamp(time.mktime(time.gmtime())),
)
with open(fileName, 'wb') as fp:
    dump(pl, fp)