python通过自定义isnumber函数判断字符串是否为数字的方法

''' isnumeric.pytest a numeric string s if it's usablefor int(s) or float(s)'''def isnumeric(s):  '''returns True if string s is numeric'''  return all(c in "0123456789.+-" for c in s)# test module ...if __name__ == '__main__':  print(isnumeric('123'))   # True  print(isnumeric('-123.45')) # True  print(isnumeric('+3.14'))  # True  print(isnumeric('$99.95'))  # False