擅长:python、mysql、java
<p>我会这样做:</p>
<pre><code>for line in input_f:
# find the positions of As in the line
positions = [n for n, letter in enumerate(line, 1) if letter == 'a']
# Create list of strings of the form "x:y"
pairs = [("%d:%d" % (i, n)) for i, n in enumerate(positions, 1)]
# Join all those strings into a single space-separated string
all_pairs = ' '.join(pairs)
# Write the string to the file, with a + sign at the beginning
# and a newline at the end
output_f.write("+ %s\n" % all_pairs)
</code></pre>
<p>您可以修改最后一行中的字符串,以控制如何在输出文件中写入该行。你知道吗</p>