Python argparse模块使用方法解析

2020年02月20日作者：酸果实爱吐泡泡的鱼原文

这篇文章主要介绍了Python argparse模块使用方法解析,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

1. 说明

argparse 模块是python 用于解析命令行参数和选项的标准模块。
程序定义它需要的参数，然后 argparse 模块将弄清如何从 sys.argv 解析出那些参数。
argparse 模块还会自动生成帮助和使用手册，并在用户给程序传入无效参数时报出错误信息。

2. 使用流程

使用argparse 模块配置命令行参数时，需要以下几步：

import argparse

创建 ArgumentParser() 对象

调用 add_argument() 方法添加参数

使用 parse_args() 解析添加的参数, 返回一个命名空间

参数解析完后，进行后续业务逻辑的处理

示例：

import argparse
import json

args_list = ["keywords", "keywords_from_file", "prefix_keywords", "suffix_keywords",
    "limit", "format", "color", "color_type", "usage_rights", "size",
    "exact_size", "aspect_ratio", "type", "time", "time_range", "delay", "url", "single_image",
    "output_directory", "image_directory", "no_directory", "proxy", "similar_images", "specific_site",
    "print_urls", "print_size", "print_paths", "metadata", "extract_metadata", "socket_timeout",
    "thumbnail", "thumbnail_only", "language", "prefix", "chromedriver", "related_images", "safe_search", "no_numbering",
    "offset", "no_download","save_source","silent_mode","ignore_urls"]

def user_input():
 # 创建 ArgumentParser() 对象
 config = argparse.ArgumentParser()
 # 调用 add_argument() 方法添加参数
 config.add_argument('-cf', '--config_file', help='config file name', default='', type=str, required=False)
 config_file_check = config.parse_known_args()
 object_check = vars(config_file_check[0])

 if object_check['config_file'] != '':
  records = []
  json_file = json.load(open(config_file_check[0].config_file))
  for record in range(0,len(json_file['Records'])):
   arguments = {}
   for i in args_list:
    arguments[i] = None
   for key, value in json_file['Records'][record].items():
    arguments[key] = value
   records.append(arguments)
  records_count = len(records)
 else:
  # Taking command line arguments from users
  parser = argparse.ArgumentParser()
  parser.add_argument('-k', '--keywords', help='delimited list input', type=str, required=False)
  parser.add_argument('-kf', '--keywords_from_file', help='extract list of keywords from a text file', type=str, required=False)
  parser.add_argument('-sk', '--suffix_keywords', help='comma separated additional words added after to main keyword', type=str, required=False)
  parser.add_argument('-pk', '--prefix_keywords', help='comma separated additional words added before main keyword', type=str, required=False)
  parser.add_argument('-l', '--limit', help='delimited list input', type=str, required=False)
  parser.add_argument('-f', '--format', help='download images with specific format', type=str, required=False,
       choices=['jpg', 'gif', 'png', 'bmp', 'svg', 'webp', 'ico'])
  parser.add_argument('-u', '--url', help='search with google image URL', type=str, required=False)
  parser.add_argument('-x', '--single_image', help='downloading a single image from URL', type=str, required=False)
  parser.add_argument('-o', '--output_directory', help='download images in a specific main directory', type=str, required=False)
  parser.add_argument('-i', '--image_directory', help='download images in a specific sub-directory', type=str, required=False)
  parser.add_argument('-n', '--no_directory', default=False, help='download images in the main directory but no sub-directory', action="store_true")
  parser.add_argument('-d', '--delay', help='delay in seconds to wait between downloading two images', type=int, required=False)
  parser.add_argument('-co', '--color', help='filter on color', type=str, required=False,
       choices=['red', 'orange', 'yellow', 'green', 'teal', 'blue', 'purple', 'pink', 'white', 'gray', 'black', 'brown'])
  parser.add_argument('-ct', '--color_type', help='filter on color', type=str, required=False,
       choices=['full-color', 'black-and-white', 'transparent'])
  parser.add_argument('-r', '--usage_rights', help='usage rights', type=str, required=False,
       choices=['labeled-for-reuse-with-modifications','labeled-for-reuse','labeled-for-noncommercial-reuse-with-modification','labeled-for-nocommercial-reuse'])
  parser.add_argument('-s', '--size', help='image size', type=str, required=False,
       choices=['large','medium','icon','>400*300','>640*480','>800*600','>1024*768','>2MP','>4MP','>6MP','>8MP','>10MP','>12MP','>15MP','>20MP','>40MP','>70MP'])
  parser.add_argument('-es', '--exact_size', help='exact image resolution "WIDTH,HEIGHT"', type=str, required=False)
  parser.add_argument('-t', '--type', help='image type', type=str, required=False,
       choices=['face','photo','clipart','line-drawing','animated'])
  parser.add_argument('-w', '--time', help='image age', type=str, required=False,
       choices=['past-24-hours','past-7-days','past-month','past-year'])
  parser.add_argument('-wr', '--time_range', help='time range for the age of the image. should be in the format {"time_min":"MM/DD/YYYY","time_max":"MM/DD/YYYY"}', type=str, required=False)
  parser.add_argument('-a', '--aspect_ratio', help='comma separated additional words added to keywords', type=str, required=False,
       choices=['tall', 'square', 'wide', 'panoramic'])
  parser.add_argument('-si', '--similar_images', help='downloads images very similar to the image URL you provide', type=str, required=False)
  parser.add_argument('-ss', '--specific_site', help='downloads images that are indexed from a specific website', type=str, required=False)
  parser.add_argument('-p', '--print_urls', default=False, help="Print the URLs of the images", action="store_true")
  parser.add_argument('-ps', '--print_size', default=False, help="Print the size of the images on disk", action="store_true")
  parser.add_argument('-pp', '--print_paths', default=False, help="Prints the list of absolute paths of the images",action="store_true")
  parser.add_argument('-m', '--metadata', default=False, help="Print the metadata of the image", action="store_true")
  parser.add_argument('-e', '--extract_metadata', default=False, help="Dumps all the logs into a text file", action="store_true")
  parser.add_argument('-st', '--socket_timeout', default=False, help="Connection timeout waiting for the image to download", type=float)
  parser.add_argument('-th', '--thumbnail', default=False, help="Downloads image thumbnail along with the actual image", action="store_true")
  parser.add_argument('-tho', '--thumbnail_only', default=False, help="Downloads only thumbnail without downloading actual images", action="store_true")
  parser.add_argument('-la', '--language', default=False, help="Defines the language filter. The search results are authomatically returned in that language", type=str, required=False,
       choices=['Arabic','Chinese (Simplified)','Chinese (Traditional)','Czech','Danish','Dutch','English','Estonian','Finnish','French','German','Greek','Hebrew','Hungarian','Icelandic','Italian','Japanese','Korean','Latvian','Lithuanian','Norwegian','Portuguese','Polish','Romanian','Russian','Spanish','Swedish','Turkish'])
  parser.add_argument('-pr', '--prefix', default=False, help="A word that you would want to prefix in front of each image name", type=str, required=False)
  parser.add_argument('-px', '--proxy', help='specify a proxy address and port', type=str, required=False)
  parser.add_argument('-cd', '--chromedriver', help='specify the path to chromedriver executable in your local machine', type=str, required=False)
  parser.add_argument('-ri', '--related_images', default=False, help="Downloads images that are similar to the keyword provided", action="store_true")
  parser.add_argument('-sa', '--safe_search', default=False, help="Turns on the safe search filter while searching for images", action="store_true")
  parser.add_argument('-nn', '--no_numbering', default=False, help="Allows you to exclude the default numbering of images", action="store_true")
  parser.add_argument('-of', '--offset', help="Where to start in the fetched links", type=str, required=False)
  parser.add_argument('-nd', '--no_download', default=False, help="Prints the URLs of the images and/or thumbnails without downloading them", action="store_true")
  parser.add_argument('-iu', '--ignore_urls', default=False, help="delimited list input of image urls/keywords to ignore", type=str)
  parser.add_argument('-sil', '--silent_mode', default=False, help="Remains silent. Does not print notification messages on the terminal", action="store_true")
  parser.add_argument('-is', '--save_source', help="creates a text file containing a list of downloaded images along with source page url", type=str, required=False)
  # 使用 parse_args() 解析添加的参数
  # 默认的 args 的结果：
  # Namespace(aspect_ratio=None, chromedriver=None, color=None, color_type=None, delay=None, exact_size=None, extract_metadata=False, format=None, ignore_urls=False, image_directory=None, keywords=None, keywords_from_file=None, language=False, limit=None, metadata=False, no_directory=False, no_download=False, no_numbering=False, offset=None, output_directory=None, prefix=False, prefix_keywords=None, print_paths=False, print_size=False, print_urls=False, proxy=None, related_images=False, safe_search=False, save_source=None, silent_mode=False, similar_images=None, single_image=None, size=None, socket_timeout=False, specific_site=None, suffix_keywords=None, thumbnail=False, thumbnail_only=False, time=None, time_range=None, type=None, url=None, usage_rights=None)
  args = parser.parse_args() # 返回一个命名空间
  arguments = vars(args) # 返回 args 的属性和属性值的字典
  # arguments 的结构：
  # {'image_directory': None, 'print_urls': False, 'usage_rights': None, 'color': None, 'socket_timeout': False, 'time_range': None, 'chromedriver': None, 'prefix': False, 'extract_metadata': False, 'keywords': None, 'no_numbering': False, 'size': None, 'keywords_from_file': None, 'print_paths': False, 'no_download': False, 'delay': None, 'similar_images': None, 'specific_site': None, 'thumbnail_only': False, 'type': None, 'thumbnail': False, 'metadata': False, 'related_images': False, 'format': None, 'silent_mode': False, 'print_size': False, 'color_type': None, 'exact_size': None, 'no_directory': False, 'suffix_keywords': None, 'single_image': None, 'offset': None, 'output_directory': None, 'language': False, 'url': None, 'prefix_keywords': None, 'save_source': None, 'ignore_urls': False, 'safe_search': False, 'limit': None, 'time': None, 'aspect_ratio': None, 'proxy': None}
  records = []
  records.append(arguments)
 return records

3. 参数说明

add_argument() 函数每个参数解释如下:

name or flags - 选项字符串的名字或者列表，例如 foo 或者 -f, --foo。
action - 命令行遇到参数时的动作，默认值是 store。
store_const，表示赋值为const；
append，将遇到的值存储成列表，也就是如果参数重复则会保存多个值;
append_const，将参数规范中定义的一个值保存到一个列表；
count，存储遇到的次数；此外，也可以继承 argparse.Action 自定义参数解析；
nargs - 应该读取的命令行参数个数，可以是具体的数字，或者是?号，当不指定值时对于 Positional argument 使用 default，对于 Optional argument 使用 - - const；或者是 * 号，表示 0 或多个参数；或者是 + 号表示 1 或多个参数。
const - action 和 nargs 所需要的常量值。
default - 不指定参数时的默认值。
type - 命令行参数应该被转换成的类型。
choices - 参数可允许的值的一个容器。
required - 可选参数是否可以省略 (仅针对可选参数)。
help - 参数的帮助信息，当指定为 argparse.SUPPRESS 时表示不显示该参数的帮助信息.
metavar - 在 usage 说明中的参数名称，对于必选参数默认就是参数名称，对于可选参数默认是全大写的参数名称.
dest - 解析后的参数名称，默认情况下，对于可选参数选取最长的名称，中划线转换为下划线.

4. 位置参数设置

以上描述的是可选参数的使用，下面描述位置参数的设置，设置了位置参数后，调用脚本时必须要传入对应的值

import argparse
 
parser = argparse.ArgumentParser()
parser.add_argument('a', type=int, help='display an integer param')
args = parser.parse_args()
 
print(args.a)

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