"""Download flags of countries with error handling.

"""

import collections

import requests

import tqdm

from flag2_common import main, save_flag, HTTPStatus, Result

DEFAULT_CONCUR_REQ = 1

MAX_CONCUR_REQ = 1

# BEGIN FLAGS2_BASIC_HTTP_FUNCTIONS

def get_flag(base_url, cc):

url = '{}/{cc}/{cc}.gif'.format(base_url, cc=cc.lower())

resp = requests.get(url)

if resp.status_code != 200: #1 如果 status_code 不是 200, 就用 raise_for_status 向外抛出异常

resp.raise_for_status()

return resp.content

#注意通过base_url和cc来获得下载页面

def download_one(cc, base_url, verbose=False):

try:

image = get_flag(base_url, cc)

except requests.exceptions.HTTPError as exc: #2 捕捉HTTPError异常, 并且对404做特殊处理(status_code是404的异常不会被抛出)

res = exc.response

if res.status_code == 404:

status = HTTPStatus.not_found #3

msg = 'not found'

else: #4 其他异常向外抛出

raise

else:

save_flag(image, cc.lower() + '.gif')

status = HTTPStatus.ok

msg = 'OK'

if verbose:

print(cc, msg)

return Result(status, cc) # 注意返回的数据结构, 值得借鉴!

# END FLAGS2_BASIC_HTTP_FUNCTIONS

# BEGIN FLAGS2_DOWNLOAD_MANY_SEQ

def download_many(cc_list, base_url, verbose, max_req):

counter = collections.Counter() #1 对download的结果做统计: ok, not_found 和 error

cc_iter = sorted(cc_list) #2

if not verbose:

cc_iter = tqdm.tqdm(cc_iter) #3

for cc in cc_iter: #4 主循环

try:

res = download_one(cc, base_url, verbose) #5

except requests.exceptions.HTTPError as exc: #6 HTTP相关的error, 这些error由 get_flag抛出并且没有被donwload_one处理的, 会在这里处理.

error_msg = 'HTTP error {res.status_code} - {res.reason}'

error_msg = error_msg.format(res=exc.response)

except requests.exceptions.ConnectionError as exc: #7 其他网络相关的异常在这里处理, 非网络相关的异常会终止脚本运行

error_msg = 'Connection error'

else: #8 如果没有异常就接受 download_one 函数返回的状态

error_msg = ''

status = res.status

if error_msg:

status = HTTPStatus.error #9

counter[status] +=1 #10 统计返回的状态

if verbose and error_msg: #11

print('*** Error for {}:{}'.format(cc, error_msg))

return counter #12

# END FLAGS2_DOWNLOAD_MANY_SEQ

if __name__ == '__main__':

main(download_many, DEFAULT_CONCUR_REQ, MAX_CONCUR_REQ)