Python程序中用csv模塊來操作csv文件的基本使用教程

更新時間：2016年03月03日 14:54:56 作者：Blue Wish

這篇文章主要介紹了Python程序中用csv模塊來操作csv文件的基本使用教程,csv文件中也是格式化的數(shù)據(jù),只不過csv本身沒有XML和JSON那么流行...需要的朋友可以參考下

CSV全稱為“Comma Separated Values”,是一種格式化的文件，由行和列組成，分隔符可以根據(jù)需要來變化。
如下面為一csv文件：

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

csv可以比較方便的在不同應(yīng)用之間遷移數(shù)據(jù)。可以將數(shù)據(jù)批量導(dǎo)出為csv格式，然后倒入到其他應(yīng)用程序中。很多應(yīng)用中需要導(dǎo)出報表，也通常用csv格式導(dǎo)出，然后用Excel工具進行后續(xù)編輯。

打印發(fā)行日期及標題，逐行處理：

for line in open("samples/sample.csv"):
  title, year, director = line.split(",")
  print year, title

使用csv模塊處理：

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

改變分隔符

創(chuàng)建一csv.excel的子類，并修改分隔符為”;”

# 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

如果僅僅僅是改變一兩個參數(shù)，則可以直接在reader參數(shù)中設(shè)置，如下：

# File: csv-example-3.py
 
import csv
 
reader = csv.reader(open("samples/sample.skv"), delimiter=";")
 
for title, year, director in reader:
  print year, title

將數(shù)據(jù)存為CSV格式

通過csv.writer來生成一csv文件。

# 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)

實例

下面我們來看一個比較完整的例子，代碼說明在注釋中：

import csv


# dialect是訪問csv文件時需要指定的參數(shù)之一，用來確定csv文件的數(shù)據(jù)格式
# 下面這個函數(shù)列舉系統(tǒng)支持的dialect有哪些，默認值是'excel'，用戶也可
# 以從Dialect派生一個類，使用該類的實例作為dialect參數(shù)。
print csv.list_dialects()


def test_writer():
  # csv文件必須以二進制方式open
  with open('eggs.csv', 'wb') as csvfile:
    spamwriter = csv.writer(csvfile)
    spamwriter.writerow(['Spam'] * 5 + ['Baked Beans'])
    spamwriter.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])


def test_reader():
  with open('eggs.csv', 'rb') as csvfile:
    spamreader = csv.reader(csvfile)
    for row in spamreader:
      print row


# sniffer 用來推斷csv文件的格式，不是很準確
def test_sniffer():
  with open('eggs.csv', 'wb') as csvfile:
    spamwriter = csv.writer(csvfile, delimiter=' ')

    spamwriter.writerow(['Spam'] * 2 + ['Baked Beans'])
    spamwriter.writerow(['Spam', 'Lovely Spam', 'Wonderful Spam'])

  # 通常你需要指定與寫入者相同的文件格式才能正確的讀取數(shù)據(jù)
  with open('eggs.csv', 'rb') as csvfile:
    spamreader = csv.reader(csvfile, delimiter=' ')
    for row in spamreader:
      print ', '.join(row)

  # 如果不知道文件格式，sniffer就可以派上用場了
  with open('eggs.csv', 'rb') as csvfile:
    # 用sniffer推斷文件格式，從而得到dialect
    dialect = csv.Sniffer().sniff(csvfile.read(1024))
    print dialect.delimiter, dialect.quotechar

    # 文件重新移動到頭部
    csvfile.seek(0)

    # 用推斷出來的dialect創(chuàng)建reader
    reader = csv.reader(csvfile, dialect)

    for row in reader:
      print ', '.join(row)

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