最佳答案
如果输入中不存在某个字符,例如X,只是：
原文链接：https://www.f2er.com/python/439540.htmlmy $size = 20;
my $count = 20;
my $mark = 'X';
my $input = 'CCACGCATTTTTGTTCATTGTTCTGGCTTCTTACAAGGTTCAGTAGACTTTGTAACACAGTTGTGTCTCTCACAGATTGGCAGATGTTTGGTAAAGGATTGACTTTTCAGCCAACTCATGGGAAAGTGAAATAATGTAAAAAACAGGAAGAATACAGTTTTAGGCCTTTCAAGTGAGGCATGGCTTTCAGCTCTTGGCAAGAACAGGCAAGGAGATGCAAGTTTTAGGACTCTAAGAGGCTAGGCTTTTCAAAGTGCTTCTCTCCCCTTCACCCTCCTTCAGTTACAGCACCAAGCACCACCGAGGTGTTACCTGCAGCCTCACTCTCTACCTGGTTGTGGGATCCTGCCACTTCCTTAACCCACACTGAGTTCCTTGTGGTTCACAGGGTCACACAGAGGGCTGTAGAGATACAAAAGATATATGTGATTTTATATCACCTATCATATGAAGATATATTTATAAAATAGGAAACATATTAACCACTTATCATTTTATATATTTATGGTTTTATGTGTCAAAAATATATTGTTTCATGTATGTATTAAAGGATAAGTATGTATAAGAGGTTTTATAGATGTGTAAAATTATATATTTATACGTATCTTTACAAATTTAAGAATAAAGGAAGGAAAATTCTCAAAGAGGAATTCAGATATCAAGCAGTGCCCTTTGACCAAGAGCCTTGGTTACAACATACCTACAAAAGTGAACTATCATTGAAAGACCTATGGACACTGGATTTCTCTTTCCTTATTTAGAAGGGCAGTCTGTGTCTTGGAAAAGCATACAGTTTGTTGTATCTTGCTGGACAACAGGAGTCA';
if (2*$size*$count-$size-$count >= length($input)) {
die "selection may not complete; choose a shorter length or fewer substrings,or provide a longer input string\n";
}
my @substrings;
while (@substrings < $count) {
my $pos = int rand(length($input)-$size+1);
push @substrings,substr($input,$pos,$size,$mark x $size)
if substr($input,$size) !~ /\Q$mark/;
}