Python 循环中某些函数的全局变量改变但其他函数不改变

Question

我敢肯定之前有人回答过类似的问题，但这些帖子似乎已在有关全局变量和循环的更热门问题中丢失了。

我想做的是编写一个循环来单步执行 Google 分析 API，一次提取一天的数据。我敢肯定已经有一些软件包可以做到这一点，但这对我来说是一种学习经验。

我卡住的地方是我的循环似乎进行了正确的天数，但是发送到 GA 报告 API (V4) 的实际请求没有使用全局变量更新，即使一个简单的 print() 似乎表明它确实更新了。

这是我的代码：

# Reporting API V4

from apiclient.discovery import build
from oauth2client.service_account import ServiceAccountCredentials

# Import JSON
import json

# Open JSON config file
jsonConfig = open("config.json", "r")

# Parse the JSON file
configRead = json.loads(jsonConfig.read())

# Define global vars

SCOPES = ['https://www.googleapis.com/auth/analytics.readonly']
KEY_FILE_LOCATION = configRead['keyFileLocation']
VIEW_ID = 12345678 # made up for this exercise

startDate = 732
endDate = 732

# Define report #1
request1 = {
        'reportRequests': 
        [
          {
            'viewId': VIEW_ID,
            'dateRanges': 
            [
              {
                'startDate': f'{startDate}daysAgo',
                'endDate': f'{endDate}daysAgo'
              }
            ],
            'metrics': 
            [
              {
                'expression': 'ga:sessions'
              }
            ],
            'dimensions': 
            [
              {
                'name': 'ga:date'
              }
            ],
            'pageSize': 1
          }
        ]
      }

def initialize_analyticsreporting():
  # Initializes an Analytics Reporting API V4 service object.
  # Returns: An authorized Analytics Reporting API V4 service object.

  credentials = ServiceAccountCredentials.from_json_keyfile_name(
      KEY_FILE_LOCATION, SCOPES)

  # Build the service object
  analytics = build('analyticsreporting', 'v4', credentials=credentials)

  return analytics


def get_report(analytics):
  # Queries the Analytics Reporting API V4.
  # Args: _ analytics _ : An authorized Analytics Reporting API V4 service object.
  # Returns: The Analytics Reporting API V4 response.
  global startDate
  global endDate
  global request1

  return analytics.reports().batchGet(
      body=request1
      ).execute()

def print_response(response):

  # Parses and prints the Analytics Reporting API V4 response.
  # Args: _ response _ : An Analytics Reporting API V4 response.

  for report in response.get('reports', []):
    columnHeader = report.get('columnHeader', {})
    dimensionHeaders = columnHeader.get('dimensions', [])
    metricHeaders = columnHeader.get('metricHeader', {}).get('metricHeaderEntries', [])

    for row in report.get('data', {}).get('rows', []):
      dimensions = row.get('dimensions', [])
      dateRangeValues = row.get('metrics', [])

      for header, dimension in zip(dimensionHeaders, dimensions):
        print(header + ': ', dimension)

      for i, values in enumerate(dateRangeValues):
        for metricHeader, value in zip(metricHeaders, values.get('values')):
          print(metricHeader.get('name') + ':', value)


def main():
  global startDate
  global endDate

  analytics = initialize_analyticsreporting()
  while startDate >= 725:
    response = get_report(analytics)
    print(f'{startDate}daysAgo')
    print_response(response)
    startDate -= 1
    endDate -= 1
  print("Done now, cheers")

if __name__ == '__main__':
  main()

在那个具体的例子中，它在循环时获取 startDate 和 endDate 在 request1 内更新。

目前的输出：

732daysAgo
ga:date:  20181123
ga:sessions: 2887
731daysAgo
ga:date:  20181123
ga:sessions: 2887
730daysAgo
ga:date:  20181123
ga:sessions: 2887
729daysAgo
ga:date:  20181123
ga:sessions: 2887
728daysAgo
ga:date:  20181123
ga:sessions: 2887
727daysAgo
ga:date:  20181123
ga:sessions: 2887
726daysAgo
ga:date:  20181123
ga:sessions: 2887
725daysAgo
ga:date:  20181123
ga:sessions: 2887
Done now, cheers

知道可能是什么问题吗？

Answer 1

问题是您希望根据 startDate 和 endDate 的值动态生成 request1，但您目前只在程序的开头，因此它永远不会根据这些变量中的任何一个更改其定义。

要 request1 是动态的，您可以创建一个 returns 请求的函数：

startDate = 732 
endDate = 732
VIEW_ID = 12345678

def get_request1():
    global startDate
    global endDate
    global VIEW_ID
    
    return {
    'reportRequests': 
    [
      {
        'viewId': VIEW_ID,
        'dateRanges': 
        [
          {
            'startDate': f'{startDate}daysAgo',
            'endDate': f'{endDate}daysAgo'
          }
        ],
        'metrics': 
        [
          {
            'expression': 'ga:sessions'
          }
        ],
        'dimensions': 
        [
          {
            'name': 'ga:date'
          }
        ],
        'pageSize': 1
      }
    ]
  }

因此，每次调用get_request1()，其返回值将始终包含当前的开始日期和结束日期值。

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