Python => ValueError: 不支持的格式字符 'Y' (0x59)

Question

我不明白 Y 的 ValueError。我用 % 轉義...

table = town+"_history"
db.execute("SELECT DATE_FORMAT(snapdate,'%%Y-%%m-%%d') AS date, SUM( population ) AS accountpopulation, count( blockid ) AS number_block FROM %s WHERE blockid =%%s GROUP BY snapdate ORDER BY snapdate DESC LIMIT 7" % table, (blockid))

Answer 1

你逃脫%%但隨后第一次使用字符串作為格式：

"...." % table,

返回一個新字符串，其中%%轉義百分比由單個%字符替換。 MySQL數據庫適配器（AB）使用字符串格式化% 了 ，所以它會采取輸出，並希望能夠填補%s插槽逃脫SQL文本。 正是在那里，SQL語句的'%Y-%m-%d'部分再次被解釋為字符串格式並且拋出錯誤。

解決方案是將倍增加倍：

db.execute("SELECT DATE_FORMAT(snapdate,'%%%%Y-%%%%m-%%%%d') AS date, SUM( population ) AS accountpopulation, count( blockid ) AS number_block FROM %s WHERE blockid = %%s GROUP BY snapdate ORDER BY snapdate DESC LIMIT 7" % table, (blockid,))

或者使用str.format()來避免雙重轉義：

db.execute("SELECT DATE_FORMAT(snapdate,'%%Y-%%m-%%d') AS date, SUM( population ) AS accountpopulation, count( blockid ) AS number_block FROM {0} WHERE blockid = %s GROUP BY snapdate ORDER BY snapdate DESC LIMIT 7".format(table), (blockid,))

這里{0}被表名替換， %%轉義保持不變; 數據庫適配器將使用%s插槽填充blockid參數並返回一個SQL語句，其中%%轉義符轉換為單個%字符。

Answer 2

最后，@ Martijn Pieters你完全正確。 謝謝你的有用答案。 另一個錯誤來自SUM和COUNT。 在處理JSON時，Python有時會以瘋狂的方式運行。 所以完整的答案是：

db.execute("SELECT DATE_FORMAT(snapdate,'%%%%Y-%%%%m-%%%%d') AS date, CAST(SUM( population ) AS CHAR ) AS accountpopulation, CAST(count( blockid ) AS CHAR) AS number_block FROM %s WHERE blockid = %%s GROUP BY snapdate ORDER BY snapdate DESC LIMIT 7" % table, (blockid,))

Answer 3

from sqlalchemy import text sql = "SELECT DATE_FORMAT(snapdate,'%Y-%m-%d') AS date...." db.execute(text(sql))

Answer 4

我發現這個答案更優雅，更不凌亂。 我已經在我的代碼中使用它，沒有任何問題。