Python 2.7.1：如何打開，編輯和關閉CSV文件

Question

我無法打開文件（amount2.csv）進行更改，保存並關閉文件。

如何打開文件編輯，保存並關閉它？

import csv 

changes = { 
    '1 dozen' : '12' 
    } 
with open('amount2.csv', 'r') as f: 
reader = csv.reader(f) 
print f 
f.close() 

我的錯誤：打開文件 'amount2.csv' 模式 'R' 在0x1004656f0 （<>刪除）

Answer 1

你要打印的文件對象本身，它不會做非常有用。 你看過the documentation for the CSV module？第一個代碼示例向您展示瞭如何使用csv.reader。

Answer 2

的

<open file 'amount2.csv', mode 'r' at 0x1004656f0> 

你看到的是不是一個錯誤，但你的「打印F」的結果。爲了而是會看到文件的內容，你會做

with open('test.csv', 'rb') as f: 
    reader = csv.reader(f) 
    for row in reader: 
     # row is a list of strings 
     # use string.join to put them together 
     print ', '.join(row) 

要追加行到您的文件，而不是在Python CSV Docs

編輯做

changes = [  
    ['1 dozen','12'],                
    ['1 banana','13'],               
    ['1 dollar','elephant','heffalump'],           
    ]                    

with open('test.csv', 'ab') as f:          
    writer = csv.writer(f)              
    writer.writerows(changes) 

更多信息：

我起初誤解，你想在你的csv文件中將'1打'改爲'12'。我會先說，不用csv模塊就可以做到這一點，但這裏有一個解決方案。

import csv 

new_rows = [] # a holder for our modified rows when we make them 
changes = { # a dictionary of changes to make, find 'key' substitue with 'value' 
    '1 dozen' : '12', # I assume both 'key' and 'value' are strings 
    } 

with open('test.csv', 'rb') as f: 
    reader = csv.reader(f) # pass the file to our csv reader 
    for row in reader:  # iterate over the rows in the file 
     new_row = row  # at first, just copy the row 
     for key, value in changes.items(): # iterate over 'changes' dictionary 
      new_row = [ x.replace(key, value) for x in new_row ] # make the substitutions 
     new_rows.append(new_row) # add the modified rows 

with open('test.csv', 'wb') as f: 
    # Overwrite the old file with the modified rows 
    writer = csv.writer(f) 
    writer.writerows(new_rows) 

如果你是新來的編程和Python的最trobulesome線可能是

new_row = [ x.replace(key, value) for x in new_row ] 

，但是這僅僅是一個列表理解這實際上等同於

temp = [] 
for x in new_row: 
    temp.append(x.replace(key, value)) 
new_row = temp