某些函数的 Python 全局变量在循环中更改，但其他函数没有更改

Question

我敢肯定之前有人回答过类似的问题，但这些帖子似乎已经在关于全局变量和循环的更受欢迎的问题中丢失了。

我想要做的是编写一个循环来逐步执行 Google Analytics API，一天一次地提取数据。 我确信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 Reporting 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() 似乎表示它确实更新了。

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()

在那个特定的例子中，当它循环时，它正在获取 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request1根据startDate和endDate的值动态生成，但您目前只在程序开始时定义request1一次，因此它永远不会根据这些变量中的任何一个更改其定义。

要使request1是动态的，您可以创建一个返回请求的函数：

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开始日期和结束日期的当前值。