用于打印字典项目一次而不重复打印功能的 for 循环答案

【问题标题】：A for loop to print dictionary items once without repeating the print function用于打印字典项目一次而不重复打印功能的 for 循环
【发布时间】：2020-05-10 06:09:44
【问题描述】：

总的来说，我是 Python 和 Stackoverflow 的新手，如果我的格式很糟糕并且我不擅长英语，我很抱歉。但是我的这段代码有问题。

print('Displays prime numbers from 1 to N.')
n = int(input('Please enter a value of n: '))
for n in range(1, n + 1):
   if n >= 1:
       for i in range(2, n):
           if (n % i) == 0:
              break
       else:
           print('They are',n,end=' ')

运行时的代码结果如下所示：

Displays prime numbers from 1 to N.
Please enter a value of n:40
They are 1 They are 2 They are 3 They are 5 They are 7 They are 11 They are 13 They are 17 They are 19 They are 23 They are 29 They are 31 They are 37

但我想要这样：

Displays prime numbers from 1 to N.
Please enter a value of n:40
They are 1 2 3 5 7 11 13 17 19 23 29 31 37

【问题讨论】：

标签： python python-3.x list dictionary printing

【解决方案1】：

如果您完全确定不在循环内多次使用 print 函数，您可以设置一个标志来确定是否打印前两个单词。像这样：

print('Displays prime numbers from 1 to N.')
n = int(input('Please enter a value of n: '))
first = 'They are '
for n in range(1, n + 1):
   if n >= 1:
       for i in range(2, n):
           if (n % i) == 0:
              break
       else:
           print(first + str(n), end=' ')
           if len(first) > 0:
              first = ''

【讨论】：

【解决方案2】：

以下解决方案可能对您有所帮助

print('Displays prime numbers from 1 to N.')
n = int(input('Please enter a value of n: '))
num = [] # Create empty list
for n in range(1, n + 1):
    if n >= 1:
        for i in range(2, n):
            if (n % i) == 0:
                break
        else:
            num.append(n)
 # Write the print statement outside of the loop and use .join() function and for loop 
#to print each element of the list look like the output you have posted 
#
print('They are'," ".join(str(x) for x in num))

输出：

Displays prime numbers from 1 to N.
Please enter a value of n: 40
They are 1 2 3 5 7 11 13 17 19 23 29 31 37

【讨论】：