如何在文件中只写一次增量？

Question

我使用 for 循环读取多个文件，并使用以下代码将输出追加到单独的文件中。我正在寻找的是除了最后一次迭代之外，每次迭代都不要在 count+=1 之后打印行（请参见下文）。

output.write(file_name + ": The total number of reads with two AB sequences is " +
             str(count) + '\n')

有没有办法根据我的代码在输出文件的末尾只打印一次最后的 count+=1？

from Bio import SeqIO

files=['2_.fasta','4_.fasta']

for file_name in files:
    count=0
    with open(file_name,'r') as f:
        for record in SeqIO.parse(f,'fasta'):
            #some code
            if str(v1) in record.seq and str(v2) in record.seq:
                #some code
                out = "sample" + file_name[:1] + "_two_AB.txt"
                with open(out,'a') as output:
                    output.write(file_name + '\n')
                    output.write(">"+str(record.id) + '\n')
                    count+=1
                    output.write(file_name + ": The total number of reads with two AB sequences is " 
                                 + str(count) + '\n')

output.close()

Answer 1

希望对您有所帮助（如果我理解您的问题）：

在这段代码中，我使用了 list 和 tuple 来保存信息，例如 out，file_name、record.id 和计数。在我在 for 中使用此列表将数据复制到列表中后，到相应的文件中。

我的代码:

from Bio import SeqIO

files=['2_.fasta','4_.fasta']
my_list=[]

for file_name in files:
    count=0
    with open(file_name,'r') as f:
        for record in SeqIO.parse(f,'fasta'):
            #some code
            if str(v1) in record.seq and str(v2) in record.seq:
                #some code
                out = "sample" + file_name[:1] + "_two_AB.txt"
                with open(out,'a') as output:
                    output.write(file_name + '\n')
                    output.write(">"+str(record.id) + '\n')
                    count+=1
                    my_list.append(tuple((out,file_name,str(record.id),count)))
                    #output.write(file_name + ": The total number of reads with two AB sequences is " 
                    #             + str(count) + '\n')

    output.close()
    #Alternative
        #for idx,val enumerate(my_list):
        #    my_out=val[0] # I have out value
        #    my_file_name=[1] # I have the file_name value
        #    my_record=val[2] # I have the record.id value
        #    my_count=val[3] # I have the count value
        #    with open(my_out, 'a') as output:
        #        output.write(my_file_name + '\n')
        #        output.write(">"+ my_record + '\n')
                #output.write(my_file_name + ": The total number of reads with two AB sequences is "+ str(my_count))
        #    output.close()
    
# -1 in this list is the last file
# my_list[-1][0] Here I have out es."sample" + file_name[:1] + "_two_AB.txt"
# my_list[-1][1] Here I have the file_name
# my_list[-1][2] Here I have the record.id
# my_list[-1][3] Here I have the count    
with open(my_list[-1][0], 'a') as output: # my_list[-1][0] is the last file, I have value's "out"
     #output.write(my_list[-1][1] + '\n') #my_list[-1][1] i have my_file_name
     #output.write(">"+ my_list[-1][2] + '\n') #my_record
     output.write(my_list[-1][2] + ": The total number of reads with two AB sequences is "+ str(my_list[-1][3]))
     output.close()

如何在文件中只写一次增量？

How to write increment only once in a file?

python

append

increment