====== Python CSV文件处理/读写 ======
CSV全称为“Comma Separated Values",是一种格式化的文件，由行和列组成，分隔符可以根据需要来变化。 \\
如下面为一csv文件：

<file>
Title,Release Date,Director
And Now For Something Completely Different,1971,Ian MacNaughton
Monty Python And The Holy Grail,1975,Terry Gilliam and Terry Jones
Monty Python's Life Of Brian,1979,Terry Jones
Monty Python Live At The Hollywood Bowl,1982,Terry Hughes
Monty Python's The Meaning Of Life,1983,Terry Jones
</file>

===== 打印发行日期及标题。=====

逐行处理：
<code python>
for line in open("samples/sample.csv"):
    title, year, director = line.split(",")
    print year, title
</code>

=====使用csv模块处理：=====

<code python>
import csv
reader = csv.reader(open("samples/sample.csv"))
for title, year, director in reader:
    print year, title
</code>

=====改变分隔符=====
创建一csv.excel的子类，并修改分隔符为";"
<code python>
# File: csv-example-2.py
import csv
class SKV(csv.excel):
    # like excel, but uses semicolons
    delimiter = ";"

csv.register_dialect("SKV", SKV)
reader = csv.reader(open("samples/sample.skv"), "SKV")
for title, year, director in reader:
    print year, title
</code>

如果仅仅仅是改变一两个参数，则可以直接在reader参数中设置，如下：
<code python>
# File: csv-example-3.py

import csv

reader = csv.reader(open("samples/sample.skv"), delimiter=";")

for title, year, director in reader:
    print year, title
</code>

===== 将数据存为CSV格式 =====
通过csv.writer来生成一csv文件。
<code python>
# File: csv-example-4.py

import csv
import sys

data = [
    ("And Now For Something Completely Different", 1971, "Ian MacNaughton"),
    ("Monty Python And The Holy Grail", 1975, "Terry Gilliam, Terry Jones"),
    ("Monty Python's Life Of Brian", 1979, "Terry Jones"),
    ("Monty Python Live At The Hollywood Bowl", 1982, "Terry Hughes"),
    ("Monty Python's The Meaning Of Life", 1983, "Terry Jones")
]

writer = csv.writer(sys.stdout)

for item in data:
    writer.writerow(item)
</code>