@balibou thank you for your reply, I think exectype == 'Close' refers to the "close price" rather than close operation.
I've made a simple solution:

commissions = []

class CommInfo_My(bt.CommInfoBase):
    global commissions

    def _getcommission(self, size, price, pseudoexec):
        if commissions:
            comm = commissions[0] * size * price

        if not pseudoexec:
            commissions.pop(0)

        return comm

def next(self):
    if condition1:
        commissions.append(0.0045)
        self.buy()
    elif condition2:
        commissions.append(0.009)
        self.close()

cerebro.broker.addcommissioninfo(strategyDraft.CommInfo_My())

@balibou thank you for your reply, I think exectype == 'Close' refers to the "close price" rather than close operation.
I've made a simple solution:

commissions = []

class CommInfo_My(bt.CommInfoBase):
    global commissions

    def _getcommission(self, size, price, pseudoexec):
        if commissions:
            comm = commissions[0] * size * price

        if not pseudoexec:
            commissions.pop(0)

        return comm

def next(self):
    if condition1:
        commissions.append(0.0045)
        self.buy()
    elif condition2:
        commissions.append(0.009)
        self.close()

cerebro.broker.addcommissioninfo(strategyDraft.CommInfo_My())

I would like to set different commissions depending on the order type, if it is buy/sell operations, it should charges a percentage comm = X, and if it is a close operation, it should charge double: 2X.

def next(self):
    if condition1:
        self.broker.setcommission(0.0045)
        self.buy()
    elif condition2:
        self.broker.setcommission(0.009)
        self.close()

Is there any way through commission scheme or other method to do this?
Thank you in advance.