ParseFromString returning filesize of binary file, not data

Question

I am trying to get the data from a binary file (specifically OnlineSequencer's new sequence file format) using Google protocol buffer, but all it's printing is the file size. I have compiled both the .proto files used by it to python scripts: sequence.proto:

    syntax = "proto3";

import "note_type.proto";

message Note {
  NoteType type = 1;
  float time = 2;
  float length = 3;
  int32 instrument = 4;
  float volume = 5;
}

message Marker {
  float time = 1;
  int32 setting = 2;
  int32 instrument = 3;
  float value = 4;
  bool blend = 5;
}

message InstrumentSettings {
  float volume = 1;
  bool delay = 2;
  bool reverb = 3;
  float pan = 4;
  bool enable_eq = 5;
  float eq_low = 6;
  float eq_mid = 7;
  float eq_high = 8;
  float detune = 9;
}

message SequenceSettings {
  int32 bpm = 1;
  int32 time_signature = 2;
  map<int32, InstrumentSettings> instruments = 3;
  // Storing volume as (1 - volume) so it defaults to volume=1.
  float one_minus_volume = 4;
}

message Sequence {
  SequenceSettings settings = 1;
  repeated Note notes = 2;
  repeated Marker markers = 3;
}

note_type.proto:

syntax = "proto3";

enum NoteType {
  C0 = 0;
  CS0 = 1;
  D0 = 2;
  DS0 = 3;
  E0 = 4;
  F0 = 5;
  FS0 = 6;
  G0 = 7;
  GS0 = 8;
  A0 = 9;
  AS0 = 10;
  B0 = 11;
  C1 = 12;
  CS1 = 13;
  D1 = 14;
  DS1 = 15;
  E1 = 16;
  F1 = 17;
  FS1 = 18;
  G1 = 19;
  GS1 = 20;
  A1 = 21;
  AS1 = 22;
  B1 = 23;
  C2 = 24;
  CS2 = 25;
  D2 = 26;
  DS2 = 27;
  E2 = 28;
  F2 = 29;
  FS2 = 30;
  G2 = 31;
  GS2 = 32;
  A2 = 33;
  AS2 = 34;
  B2 = 35;
  C3 = 36;
  CS3 = 37;
  D3 = 38;
  DS3 = 39;
  E3 = 40;
  F3 = 41;
  FS3 = 42;
  G3 = 43;
  GS3 = 44;
  A3 = 45;
  AS3 = 46;
  B3 = 47;
  C4 = 48;
  CS4 = 49;
  D4 = 50;
  DS4 = 51;
  E4 = 52;
  F4 = 53;
  FS4 = 54;
  G4 = 55;
  GS4 = 56;
  A4 = 57;
  AS4 = 58;
  B4 = 59;
  C5 = 60;
  CS5 = 61;
  D5 = 62;
  DS5 = 63;
  E5 = 64;
  F5 = 65;
  FS5 = 66;
  G5 = 67;
  GS5 = 68;
  A5 = 69;
  AS5 = 70;
  B5 = 71;
  C6 = 72;
  CS6 = 73;
  D6 = 74;
  DS6 = 75;
  E6 = 76;
  F6 = 77;
  FS6 = 78;
  G6 = 79;
  GS6 = 80;
  A6 = 81;
  AS6 = 82;
  B6 = 83;
  C7 = 84;
  CS7 = 85;
  D7 = 86;
  DS7 = 87;
  E7 = 88;
  F7 = 89;
  FS7 = 90;
  G7 = 91;
  GS7 = 92;
  A7 = 93;
  AS7 = 94;
  B7 = 95;
  C8 = 96;
  CS8 = 97;
  D8 = 98;
  DS8 = 99;
  E8 = 100;
  F8 = 101;
  FS8 = 102;
  G8 = 103;
  GS8 = 104;
  A8 = 105;
  AS8 = 106;
  B8 = 107;
}

Main script:

import sequence_pb2
f = open('./test.sequence', 'rb')
print(f)
sequence = sequence_pb2.Sequence()
print(sequence)
print(sequence.ParseFromString(f.read()))
f.close()

I'm not sure why this isn't working. If I have a file in the script's folder, it just prints the size of the file, in bytes. I've never really done much with binary files in the past, so I'm pretty new to this kind of stuff. If I could get help with this, that would be great.

Answer 1

The ParseFromString method returns the number of bytes that were parsed (see doc), and stores the contents in the instance itself.

You probably want to look at the sequence object's contents after parsing:

sequence = sequence_pb2.Sequence()
sequence.ParseFromString(f.read())
print(sequence)