讀寫CSV資料

讀csv檔案

將資料讀取為一個元祖的序列

import csv
with open('stocks.csv') as f:
    f_csv = csv.reader(f)
    headers = next(f_csv)
    for row in f_csv:
        # Process row
        ...

row是一個列表。訪問欄位可以用下標。
匯入到sqlalchemy時：

header = Node.__table__.columns.keys()
with open(node_csv[0],encoding='utf-8') as csvfile:
    reader = csv.reader(csvfile)
    for item in reader:
        #通過node_id匯入，修改物件屬性值
        if 'node_id' in header:
            node_id = item[header.index('node_id')]
            b_query = Node.query.filter_by(node_id=node_id)
        if b_query.count():
            b_node = b_query.one()
            for index in range(1,len(header)):
               setattr(b_node, header[index], item[index])
               db.session.commit()
 

寫csv檔案

將SQLAlchemy的資料匯出成csv檔案。
使用UTF-8編碼，header從Node表中生成，將需要匯出的專案從表中查詢得到後，寫入一行資料，資料是物件record的header屬性值。

• 使用示例

outpath = os.path.join(db_folder, "backup_node_%s.csv"%projectid)
outfile = open(outpath, "w", encoding="utf-8", newline="")

outcsv = csv.writer(outfile)
header = Node.__table__.columns.keys()
records = Node.query.filter_by(project_id=projectid).all()
for record in records:
    outcsv.writerow([getattr(record, c) for c in header ])
outfile.close()
 

引用

• 讀寫CSV資料
• Reading a UTF8 CSV file with Python
• How to write UTF-8 in a CSV file