Python通用循环的构造方法实例分析

def main():
  sum =0.0
  count =0
  moredata =\'yes\'  #字符串
  while moredata[0] ==\'y\': #获取字符串第一个字符，true执行下面的
    x =eval(input(\'enter a number>>\'))
    sum =sum+x
    count = count +1
    moredata =input(\"你有更多的number(yes or no)\")
  print(\"pingjunshushi:\\n\",sum/count)
main()
enter a number >>3
你有更多的number(yesor no)y
enter a number >>4
你有更多的number(yesor no)n
pingjunshushi:
 3.5

def main():
  sum =0
  count =0
  xStr = input(\"enter a number\")
  while xStr != \"\":  #空字符串
    x = eval(xStr)  #转换字符串为数字的过成
    sum = sum + x
    count =count +1
    xStr = input(\"enter a number :\")
  print(\"average is\",sum/count)
main()
enter a number6
enter a number :6
enter a number :6
enter a number :  这里确认输入不是哨兵空字符才将输入字符串转换为数字
average is 6.0

def main():
  fileName = input(\"file denumber:\") #这个相当于一个文件
  infile = open(fileName,\'r\') #open(文件名，方式\'r\'/\'w\')函数用来打开这个文件的一行保存在infile列表（相当一个数组）中
  sum =0
  count = 0
  for line ininfile:   #循环变量line遍历文件的每一行（文件每一行已经保存在infile列表中），将每一行执行下面的代码
    sum = sum+eval(line)
    count = count +1
  print(\"aveage is:\",sum/count)
main()

line=infile.readline()
while line != \"\":
#处理每一行
line =infile.readline()

while True:
  try:
    x = int(input(\"输入一个数字：\"))
    break
  except ValueError:
    print(\"重新输入：\")

dict1={\"name\":\"liyue\"}
dict2=dict1.copy()
print(\"dict2 is:\",str(dict2))