--- a/fasta_filter_by_length.py	Tue Dec 17 13:13:32 2019 -0500
+++ b/fasta_filter_by_length.py	Sun Mar 01 07:24:42 2020 -0500
@@ -5,48 +5,50 @@
 Return sequences whose lengths are within the range.
 """
 
-import sys, os
+import sys
 
-assert sys.version_info[:2] >= ( 2, 4 )
+assert sys.version_info[:2] >= (2, 4)
 
-def stop_err( msg ):
-    sys.stderr.write( msg )
-    sys.exit()
+
+def stop_err(msg):
+    sys.exit(msg)
+
 
 def __main__():
     input_filename = sys.argv[1]
     try:
-        min_length = int( sys.argv[2] )
-    except:
-        stop_err( "Minimal length of the return sequence requires a numerical value." )
+        min_length = int(sys.argv[2])
+    except Exception:
+        stop_err("Minimal length of the return sequence requires a numerical value.")
     try:
-        max_length = int( sys.argv[3] )
-    except:
-        stop_err( "Maximum length of the return sequence requires a numerical value." )
+        max_length = int(sys.argv[3])
+    except Exception:
+        stop_err("Maximum length of the return sequence requires a numerical value.")
     output_filename = sys.argv[4]
-    output_handle = open( output_filename, 'w' )
-    tmp_size = 0 #-1
+    tmp_size = 0  # -1
     tmp_buf = ''
     at_least_one = 0
-    for line in file(input_filename):
-        if not line or line.startswith('#'):
-            continue
-        if line[0] == '>':
-            if min_length <= tmp_size <= max_length or (min_length <= tmp_size and max_length == 0):
-                output_handle.write(tmp_buf)
-                at_least_one = 1
-            tmp_buf = line
-            tmp_size = 0                                                       
-        else:
-            if max_length == 0 or tmp_size <= max_length:
-                tmp_size += len(line.rstrip('\r\n'))
-                tmp_buf += line
-    # final flush of buffer
-    if min_length <= tmp_size <= max_length or (min_length <= tmp_size and max_length == 0):
-        output_handle.write(tmp_buf.rstrip('\r\n'))
-        at_least_one = 1
-    output_handle.close()
+    with open(output_filename, 'w') as output_handle, open(input_filename, 'r') as input_handle:
+        for line in input_handle:
+            if not line or line.startswith('#'):
+                continue
+            if line[0] == '>':
+                if min_length <= tmp_size <= max_length or (min_length <= tmp_size and max_length == 0):
+                    output_handle.write(tmp_buf)
+                    at_least_one = 1
+                tmp_buf = line
+                tmp_size = 0
+            else:
+                if max_length == 0 or tmp_size <= max_length:
+                    tmp_size += len(line.rstrip('\r\n'))
+                    tmp_buf += line
+        # final flush of buffer
+        if min_length <= tmp_size <= max_length or (min_length <= tmp_size and max_length == 0):
+            output_handle.write(tmp_buf.rstrip('\r\n'))
+            at_least_one = 1
     if at_least_one == 0:
-        print "There is no sequence that falls within your range."
+        print("There is no sequence that falls within your range.")
+
 
-if __name__ == "__main__" : __main__()
+if __name__ == "__main__":
+    __main__()