replace 不起作用；
update_per_seconds = "30"
uploadtime_per_seconds = "30"
imei_string = "1234"
### 采用 {0} format 不行
### 下面replace不行
msg = """{"rmtcmd":"set","dev":{"poll":{"timeout":10,"update":update_per_seconds,"delay":15,"uploadtime":uploadtime_per_seconds,"uploadtype":1,"uploadchange":1,"timestamp":1,"timeoutmode":2,"array":0,"y_trigger":1,"prefix":"","cmdcnt":4}},"imei":"imei_string"}"""
msg.replace("update_per_seconds",update_per_seconds)
msg.replace("uploadtime_per_seconds", uploadtime_per_seconds)
msg.replace("imei_string", imei_string)
print(msg)
### 下面可行
s1 = """{"rmtcmd":"set","dev":{"poll":{"timeout":10,"update":"""
s2 = ""","delay":15,"uploadtime":"""
s3 = ""","uploadtype":1,"uploadchange":1,"timestamp":1,"timeoutmode":2,"array":0,"y_trigger":1,"prefix":"","cmdcnt":4}},"imei":\""""
s4 = """\"}"""
msg = s1 + update_per_seconds + s2 + uploadtime_per_seconds + s3 + imei_string+ s4
print(msg)
