Python處理CSV檔案的方法

        與txt檔案相比，CSV（Comma Separated Value）檔案可以把資料組織的更有層次。而且CSV檔案可以被Excel讀取編輯，是以它能很友善的在不同應用之間傳遞資料。

下面給出處理CSV檔案的一些關鍵代碼：

import csv

infile = open(filename)    # For reading. Also infile = open(filename,'r')
infile.close()             # An open file locks other applications out
rows = csv.reader(infile)            # Read row

f = open(filename, 'w', newline='')  # Open for writing
csv.writer(f).writerows(rowlist)     # Write all rows at once
csv.writer(f).writerow(row)          # Write one row
f.close()
           

讀取CSV檔案并把内容添加到一個清單（list）中：

import csv

def read_csv_file1(filename):
    """Reads a CSV file and print it as a list of rows."""
    f = open(filename)
    data = []
    for row in csv.reader(f):
        data.append(row)
    print(data)   
    f.close()
           

将清單寫入CSV檔案：

def write_csv(filename):
    import csv
   
    L = [['Date', 'Name', 'Notes'], 
         ['2016/1/18', 'Martin Luther King Day', 'Federal Holiday'],
         ['2016/2/2','Groundhog Day', 'Observance'], 
         ['2016/2/8','Chinese New Year', 'Observance'], 
         ['2016/2/14','Valentine\'s Day', 'Obervance'], 
         ['2016/5/8','Mother\'s Day', 'Observance'], 
         ['2016/8/19','Statehood Day', 'Hawaii Holiday'], 
         ['2016/10/28','Nevada Day', 'Nevada Holiday']]
    
    f = open(filename, 'w', newline='')
    for item in L:
        csv.writer(f).writerow(item)
    f.close()
           

這裡open函數中使用newline=' '是為了避免在不同行之間生成多餘的空行。自己試驗一下就知道了。