Python 2.7.1：如何打开，编辑和关闭CSV文件

Question

我无法打开文件（amount2.csv）进行更改，保存并关闭文件。

如何打开文件编辑，保存并关闭它？

import csv 

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

我的错误：打开文件 'amount2.csv' 模式 'R' 在0x1004656f0 （<>删除）

Answer 1

你要打印的文件对象本身，它不会做非常有用。 你看过the documentation for the CSV module？第一个代码示例向您展示了如何使用csv.reader。

Answer 2

的

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

你看到的是不是一个错误，但你的“打印F”的结果。为了而是会看到文件的内容，你会做

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

编辑做

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：

我起初误解，你想在你的csv文件中将'1打'改为'12'。我会先说，不用csv模块就可以做到这一点，但这里有一个解决方案。

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) 

如果你是新来的编程和Python的最trobulesome线可能是

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

，但是这仅仅是一个列表理解这实际上等同于

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