Question

所以我不确定问题是否足够清楚，所以让我举个例子。

如果我有一个两行的数据库，我可以做类似的事情

if something_row_1():
    #do_something
if something_row_2():
    #do_something

但是我的代码中还有一些函数可以让您向数据库添加行。因此，您不知道在运行程序时需要多少个IF。

是否有任何方法可以在不使用SQL语法而仅使用Python的情况下执行任何操作？

编辑：我正在使用SQLite

Answer 1

我认为有可能。您可以为此使用循环和列表。

rows = get_list_of_rows_from_db()
do_something = get_do_something_list()
for r in range(0,len(r)):
    if rows[r]:
        do_something[r]

Answer 2

我不知道这是否能回答您的问题，但您可以将一套易于维护的规则放在一起，并为记录数量提供一定的灵活性。

如果我很了解您，则必须阅读数据库行，并针对每一行测试不同的条件并执行不同的操作。

在这种情况下，您可以按照以下代码进行操作：

# Suppose  you read the database and get the rows
# (Adapt your code to actual rows format)
rows = [
    ("q1", "w1", "e1", "r1"),
    ("q2", "w2", "e2", "r2"),
    ("q3", "w3", "e3", "r3"),
]


# Suppose then that the index of the row says which condition to apply, .e. you know that row1 leads to condition 1 etc...

# Then you can write a "router

# You can define tests for known conditions:

def something_row_1(row):
    # FOR EXAMPLE: (return your condition)
    return row[1] == "w1"


def something_row_2(row):
    # FOR EXAMPLE: (return your condition)
    return row[2] == "e2"


# And one for all unknown conditions
def default_test(row):
    return True  # or whatever


tests = [
    something_row_1,
    something_row_2,
]


# Define the corresponding actions:
def known_action_1(row):
    # FOR EXAMPLE: (perform your own action)
    print("Action 1 for row", row)


def known_action_2(row):
    # FOR EXAMPLE: (perform your own action)
    print("Action 2 for row", row)


def default_action(row):
    # FOR EXAMPLE: (perform your own action)
    print("Default action")


actions = [
    known_action_1,
    known_action_2,
]

# You can then route your actions
def route_actions(rows):
    for i, row in enumerate(rows):
        if i < len(tests):
            # Get the test to use
            test = tests[i]
            # Get the action
            action = actions[i]
            # Do the corresponding action
        else:
            test = default_test
            action = default_action

        if test(row):
            action(row)


route_actions(rows)

输出为：

Action 1 for row ('q1', 'w1', 'e1', 'r1')
Action 2 for row ('q2', 'w2', 'e2', 'r2')
Default action

您可以为已知行定义已知操作，为新行/未知行定义默认操作。

希望这能回答您的问题。

IF数量未知时的Python IF语句

2 个答案: