My code is meant to transform a text file in the format below:

> gene name
gene sequence

to a csv file where in each row, 1 column has a gene name and other has a gene sequence.
However, some of the gene sequences flows over to the next row.

How can I prevent this from happening?

 def parse_gene_file(input_file):
    genes = []
    with open(input_file, 'r') as file:
        gene_name = None
        gene_sequence = []
        for line in file:
            line = line.strip()
            if line.startswith('>'):
                # It means we have just finished reading the sequence of a gene.
                if gene_name is not None:
                    genes.append((gene_name, ''.join(gene_sequence)))
                    print(f"Added gene: {gene_name} with sequence: {''.join(gene_sequence)}")
                gene_name = line[1:].strip() # Set gene_name to the new gene name (strip the > and any leading/trailing whitespace)
                gene_sequence = []
            else:
                gene_sequence.append(line)
        if gene_name is not None:
            genes.append((gene_name, ''.join(gene_sequence))) # ensure the last gene is added to the genes list.
            print(f"Added gene: {gene_name} with sequence: {''.join(gene_sequence)}")
    return genes

def write_to_csv(genes, output_file):
    with open(output_file, 'w', newline='') as csvfile:
        writer = csv.writer(csvfile)
        writer.writerow(['Gene Name', 'Gene Sequence'])
        writer.writerows(genes)

def main(input_file, output_file):
    genes = parse_gene_file(input_file)
    write_to_csv(genes, output_file)

if __name__ == "__main__":
    input_file = r'C:txt'  # input file name
    output_file = r'C:csv'  # output file name
    main(input_file, output_file)