{"id":1372,"date":"2018-11-14T17:50:53","date_gmt":"2018-11-14T09:50:53","guid":{"rendered":"https:\/\/www.techcoil.com\/blog\/?p=1372"},"modified":"2018-11-17T22:31:29","modified_gmt":"2018-11-17T14:31:29","slug":"how-to-download-a-file-via-http-post-and-http-get-with-python-3-requests-library","status":"publish","type":"post","link":"https:\/\/www.techcoil.com\/blog\/how-to-download-a-file-via-http-post-and-http-get-with-python-3-requests-library\/","title":{"rendered":"How to download a file via HTTP POST and HTTP GET with Python 3 requests library"},"content":{"rendered":"

When you are building a HTTP client<\/a> with Python 3, you could be coding it to upload a file to a HTTP server<\/a> or download a file from a HTTP server. <\/p>\n

Previously, we discussed how to upload a file and some data through HTTP multipart in Python 3 using the requests library<\/a>. In this post, let's see how we can download a file via HTTP POST and HTTP GET.<\/p>\n

Downloading a file from a HTTP server endpoint via HTTP GET<\/h2>\n

Generally, downloading a file from a HTTP server<\/a> endpoint via HTTP GET consists of the following steps:<\/p>\n

    \n
  1. Construct the HTTP GET request to send to the HTTP server.<\/li>\n
  2. Send the HTTP request<\/a> and receive the HTTP Response<\/a> from the HTTP server.<\/li>\n
  3. Save the contents of the file from HTTP Response to a local file.<\/li>\n<\/ol>\n

    Python 3 function that downloads a file from a HTTP server endpoint via HTTP GET<\/h3>\n

    Given these points, we can create a Python 3 function that downloads a file from a HTTP server endpoint via HTTP GET:<\/p>\n

    \r\nimport requests\r\n\r\ndef download_file_from_server_endpoint(server_endpoint, local_file_path):\r\n\r\n    # Send HTTP GET request to server and attempt to receive a response\r\n    response = requests.get(server_endpoint)\r\n    \r\n    # If the HTTP GET request can be served\r\n    if response.status_code == 200:\r\n        \r\n        # Write the file contents in the response to a file specified by local_file_path\r\n        with open(local_file_path, 'wb') as local_file:\r\n            for chunk in response.iter_content(chunk_size=128):\r\n                local_file.write(chunk)\r\n<\/pre>\n
    As shown above, the download_file_from_server_endpoint<\/code> function expects a server endpoint and a local file path as input. After the function is called, it first uses requests.get<\/a> to get a Response<\/a> object. <\/p>\n
    When the status code in the HTTP response is a 200 OK<\/strong>, a file handler is created to write binary data to the path specified by local_file_path<\/code>. <\/p>\n
    Inside the with<\/code> statement, data is read from the HTTP response in 128-byte<\/strong> chunks and written to local_file<\/code>.<\/p>\n
    Using download_file_from_server_endpoint<\/code> to download a file from a HTTP server endpoint via HTTP GET<\/h3>\n
    After we had defined the download_file_from_server_endpoint<\/code> function, we can then use it to download a file from a HTTP server endpoint via HTTP GET. For example, if we want to download Techcoil's logo, we can call the download_file_from_server_endpoint<\/code> function as follows:<\/p>\n
    \r\ndownload_file_from_server_endpoint('https:\/\/www.techcoil.com\/ph\/img\/logo.png', 'logo.png')\r\n<\/pre>\n
    After the function call completes, you should find Techcoil's logo in the same directory as the Python script if your computer is connected to the Internet.<\/p>\n
    Downloading a file HTTP from a HTTP server endpoint via HTTP POST<\/h2>\n
    There could be cases where the client need to supply some information to the HTTP server in order to download a file. In such a situation, HTTP POST is a more appropriate HTTP method to use for downloading the file. <\/p>\n
    As with HTTP GET, downloading of a file from the HTTP server via HTTP POST consists of the following steps:<\/p>\n
      \n
    1. Construct the HTTP POST request to send to the HTTP server.<\/li>\n
    2. Send the HTTP request and receive the HTTP Response from the HTTP server.<\/li>\n
    3. Save the contents of the file from HTTP Response to a local file.<\/li>\n<\/ol>\n
      Python 3 function that downloads a file from a HTTP server endpoint via HTTP POST<\/h3>\n
      Given these points, we can create a Python 3 function that downloads a file from a HTTP server endpoint via HTTP POST:<\/p>\n
      \r\ndef download_file_from_server_endpoint(server_endpoint, local_file_path, data_dict):\r\n\r\n    # Send HTTP GET request to server and attempt to receive a response\r\n    response = requests.post(url=server_endpoint, data=data_dict)\r\n\r\n    # If the HTTP GET request can be served\r\n    if response.status_code == 200:\r\n\r\n        # Write the file contents in the response to a file specified by local_file_path\r\n        with open(local_file_path, 'wb') as local_file:\r\n            for chunk in response.iter_content(chunk_size=128):\r\n                local_file.write(chunk)\r\n\r\n<\/pre>\n
      As shown above, the download_file_from_server_endpoint<\/code> function now accepts a server endpoint, a local file path, and a data dictionary.<\/p>\n
      In this case, we had used requests.post<\/code><\/a> instead of requests.get<\/code><\/a> to get a Response<\/a>  object. In addition, we had supplied server_endpoint as the url and data_dict as the POST variables for requests.post<\/code> to construct and send the HTTP request to the server for a HTTP response.<\/p>\n
      After we had gotten the Response<\/code> object, we save the file contents in the response just like the function that downloads the file via HTTP GET.  <\/p>\n
      Using download_file_from_server_endpoint<\/code> to download a file from a HTTP server endpoint via HTTP POST<\/h3>\n
      In order to visualise how download_file_from_server_endpoint<\/code> works, we can reuse the server backend from the proof of concept that we can use jQuery to push a dynamically generated file to the web browser based on the user's input<\/a>.<\/p>\n
      Given that, we can create the following Python 3 code to use download_file_from_server_endpoint<\/code> to download a file from a HTTP server endpoint via HTTP POST:<\/p>\n
      \r\ndownload_file_from_server_endpoint('https:\/\/www.techcoil.com\/process\/proof-of-concepts\/userNameAndLuckyNumberTextFileGeneration'\r\n                                   , 'number.txt', {'visitorName': 'John Doe', 'luckyNumber': 1234})\r\n<\/pre>\n
      After the function call completes, you should find number.txt<\/code> in the same directory as the python script if your computer is connected to the Internet. In addition, number.txt should contain the following content:<\/p>\n
      \r\nHi John Doe. \r\nYou have drawn the number 1234.\r\n<\/pre>\n\n