Python 如何只跳出一个嵌套循环
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/18556403/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
how to break out of only one nested loop
提问by biohazard
I have two tab-delimited files, and I need to test every row in the first file against all the rows in the other file. For instance,
我有两个制表符分隔的文件，我需要针对另一个文件中的所有行测试第一个文件中的每一行。例如，
file1:
文件 1：
row1 c1 36 345 A
row2 c3 36 9949 B
row3 c4 36 858 C
file2:
文件2：
row1 c1 3455 3800
row2 c3 6784 7843
row3 c3 10564 99302
row4 c5 1405 1563
let's say I would like to output all the rows in (file1) for which col[3] of file1 is smaller than any (not every) col[2] of file2, given that col[1] are the same.
假设我想输出 (file1) 中 file1 的 col[3] 小于 file2 的任何（不是每个）col[2] 的所有行，因为 col[1] 是相同的。
Expected output:
预期输出：
row1 c1 36 345 A
row2 c3 36 9949 B
Since I am working in Ubuntu, I would like the input command to look like this:python code.py [file1] [file2] > [output]
由于我在 Ubuntu 中工作，我希望输入命令如下所示：python code.py [file1] [file2] > [output]
I wrote the following code:
我写了以下代码：
import sys
filename1 = sys.argv[1]
filename2 = sys.argv[2]
file1 = open(filename1, 'r')
file2 = open(filename2, 'r')
done = False
for x in file1.readlines():
col = x.strip().split()
for y in file2.readlines():
col2 = y.strip().split()
if col[1] == col2[1] and col[3] < col2[2]:
done = True
break
else: continue
print x
However, the output looks like this:
但是，输出如下所示：
row2 c3 36 9949 B
This is evident for larger datasets, but basically I always get only the last row for which the condition in the nested loop was true. I am suspecting that "break" is breaking me out of both loops. I would like to know (1) how to break out of only one of the for loops, and (2) if this is the only problem I've got here.
这对于较大的数据集很明显，但基本上我总是只得到嵌套循环中条件为真的最后一行。我怀疑“中断”使我脱离了两个循环。我想知道 (1) 如何只跳出一个 for 循环，以及 (2) 如果这是我在这里遇到的唯一问题。
采纳答案by NPE
breakand continueapply to the innermost loop.
break并continue应用于最里面的循环。
The issue is that you open the second file only once, and therefore it's only read once. When you execute for y in file2.readlines():for the second time, file2.readlines()returns an empty iterable.
问题是您只打开第二个文件一次，因此它只被读取一次。for y in file2.readlines():第二次执行时，file2.readlines()返回一个空的可迭代对象。
Either move file2 = open(filename2, 'r')into the outer loop, or use seek()to rewind to the beginning of file2.
要么移入file2 = open(filename2, 'r')外循环，要么使用seek()倒回到 的开头file2。
回答by eisoku9618
You need to parse the numeric strings to their corresponding integer values.
您需要将数字字符串解析为其相应的整数值。
You can use int('hoge')as follows.
您可以int('hoge')按如下方式使用。
import sys
filename1 = sys.argv[1]
filename2 = sys.argv[2]
with open(filename1) as file1:
for x in file1:
with open(filename2) as file2:
col = x.strip().split()
for y in file2:
col2 = y.strip().split()
if col[1] == col2[1] and int(col[3]) < int(col2[2]):
print x
