带Communicate（）函数的Python IF语句

Question

我在使用子进程的Python代码中使用了terminal命令，我试图检查communicate（）函数以检查函数返回的内容，并查看其中是否包含某些内容。我的函数current返回以下两项，具体取决于板的结果：

(b'No license plates found.\n', None) 
Plate Not Found

(b'plate0: 10 results\n    - SBG984\t confidence: 85.7017\n    -
SBG98\t confidence: 83.3453\n    - S8G984\t confidence: 78.3329\n    -
5BG984\t confidence: 76.6761\n    - S8G98\t confidence: 75.9766\n    -
SDG984\t confidence: 75.5532\n    - 5BG98\t confidence: 74.3198\n    -
SG984\t confidence: 73.3743\n    - SDG98\t confidence: 73.1969\n    -
BG984\t confidence: 71.7671\n', None) Plate Not Found

代码如下：

def read_plate():
    alpr_out = alpr_subprocess().communicate()
    print(alpr_out)
    if "No license plates found." in alpr_out:
        print ("No results!")
    elif "SBG984" in alpr_out:
        print ("Found Plate")
    else:
        print("Plate Not Found")

从这段代码可以看出，它应该打印“No results！”但是它打印的是“找不到印版”，如果函数返回的印版是SBG984，代码仍将返回“No results！”。我猜我遗漏了一些简单的东西，也许有人能发现。你知道吗

Answer 1

alpr_out是一个元组：(b'No license plates found.\n', None)

您要做的是检查子字符串是in元组的第一个元素，而不是元组本身：

def read_plate():
    alpr_out = alpr_subprocess().communicate()
    print(alpr_out)
    # Index first element with [0]
    if "No license plates found." in alpr_out[0].decode():
        print ("No results!")
    elif "SBG984" in alpr_out[0].decode():
        print ("Found Plate")
    else:
        print("Plate Not Found")