In Unix-like systems, the ASCII hyphen-minus is commonly used to specify options. The character is usually followed by one or more letters. Two hyphen-minus characters (--) often indicate that the remaining arguments should not be treated as options,
unix options bsd options gnu long options unix options, which may be grouped and must be preceded by a dash.(必须有短线-) bsd options, which may be grouped and must not be used with a dash.(bsd风格的不能有dash) gnu long options, ...must be preceded by two dashe
import osimport timeimport sys import requests#依序下载POP20_CC = ('CN IN US ID BR PK NG BD RU JP' 'MX PH VN ET EG DE IR TE CD TR').split()BASE_URL = 'http://flupy.org/data/flags'DEST_DIR = 'downloads/' def save_flag(img, filename): path = os.path.join(D
检查数据可以让程序更健壮,用术语来说就是防御性编程.检查数据的时候,有这样的两种不同的风格.LBYL:Look Before You Leap EAFP:Easier to Ask Forgiveness than Permission LBYL即事先检查.EAFP是不检查,出了问题由异常处理来处理. d = {} words = ['a','d','a','c','b','z','d'] #LBYL for w in words: if w not in d: d[w] = 0 d[w] +
EAFP:Easier to ask for forgiveness than permission 获得事后原理总是比事先得到许可要容易的多. 这个EAFP在python中表现的比较多.EAFP,This common Python coding style assumes the existence of valid keys or attributes and catches exceptions if the assumption proves false. This clean and
检查数据可以让程序更健壮,用术语来说就是防御性编程. 检查数据的时候,有这样的两种不同的风格. LBYL:Look Before You Leap EAFP:It's Easier to Ask Forgiveness than Permission LBYL即事先检查. EAFP是不检查,出了问题由异常处理来处理. 下面通过一个单词统计的例子来阐释一下. d = {} words = ['a','d','a','c','b','z','d'] #LBYL for w in words:
