Implementation:Iterative Dvc Progress

Knowledge Sources	Iterative_Dvc
Domains	User_Interface, Progress_Display
Last Updated	2026-02-10 10:00 GMT

Overview

dvc/progress.py (170 lines) defines the Tqdm class, a custom subclass of tqdm.tqdm that provides DVC-specific progress bar formatting. It features auto-disable logic based on logging level and TTY detection, byte-scale defaults, and custom bar format strings for nested and no-total scenarios.

from dvc.progress import Tqdm

Source File

Property	Value
File	`dvc/progress.py`
Lines	170
Class	`Tqdm`
Extends	`tqdm.tqdm`

Module-Level Setup

The module sets a thread-safe lock on the tqdm class using tqdm.set_lock(RLock()), ensuring that progress bar updates are safe in multi-threaded contexts.

Class: Tqdm

Tqdm is described as a "maximum-compatibility tqdm-based progressbar" that adapts its behavior to DVC's logging and output requirements.

Class Constants

Constant	Description
`BAR_FMT_DEFAULT`	Standard bar format showing percentage, description, bar, counts, timing, and rate
`BAR_FMT_DEFAULT_NESTED`	Format for nested bars with fixed 10-character bar width for alignment
`BAR_FMT_NOTOTAL`	Format used when total is unknown (no percentage, no remaining time)
`BYTES_DEFAULTS`	Default kwargs for byte-scale display: `unit="B"`, `unit_scale=True`, `unit_divisor=1024`, `miniters=1`

Constructor

def __init__(
    self,
    iterable=None,
    disable=None,
    level=logging.ERROR,
    desc=None,
    leave=False,
    bar_format=None,
    bytes=False,
    file=None,
    total=None,
    postfix=None,
    **kwargs,
)

The constructor implements several layers of smart defaults:

Byte mode: If bytes=True, merges BYTES_DEFAULTS into kwargs
Unit scale: If not in byte mode, auto-scales units when total exceeds 999
File target: Defaults to sys.stderr
Auto-disable (log level): Disables the bar if the effective logging level exceeds the specified level (default: ERROR)
Auto-disable (TTY): Disables the bar if the output file is not a TTY, unless DVC_IGNORE_ISATTY environment variable is set
Bar format selection: After initialization, selects the appropriate format:
- BAR_FMT_DEFAULT_NESTED if the bar is nested (non-zero position)
- BAR_FMT_DEFAULT for standard bars with a known total
- BAR_FMT_NOTOTAL when the total is unknown

Methods

update_msg

def update_msg(self, msg: str, n: int = 1) -> None

Convenience method that sets a message as postfix and advances the bar by n units.

set_msg

def set_msg(self, msg: str) -> None

Sets the info postfix to " {msg} |" for display between the bar and the counts.

update_to

def update_to(self, current, total=None) -> None

Sets the progress to an absolute position current (rather than an increment). Optionally updates the total. Calculates the delta from the current position and calls update().

wrap_fn

def wrap_fn(self, fn, callback=None)

Returns a wrapped version of fn that calls callback (defaults to self.update) after each invocation. Useful for adding progress tracking to any callable.

close

def close(self) -> None

Clears the info postfix and cleans up the bar format by removing the ETA display (<{remaining}) and the nested bar indicator (|{bar:10}|). Then calls the parent close().

format_dict (property)

@property
def format_dict(self) -> dict

Overrides the parent property to inject ncols_desc and ncols_info values, which dynamically fill the available display width. This is calculated by rendering the bar format with placeholder widths and measuring the remaining space. Falls back to width 1 with an empty prefix if no space remains.

as_callback

def as_callback(self) -> "TqdmCallback"

Wraps the progress bar instance in a TqdmCallback from dvc.fs.callbacks, enabling its use as a filesystem transfer callback.

Key Dependencies

Module	Usage
`tqdm.tqdm`	Base progress bar class
`dvc.env.DVC_IGNORE_ISATTY`	Environment variable to override TTY detection
`dvc.utils.env2bool`	Converts environment variable to boolean
`dvc.fs.callbacks.TqdmCallback`	Callback adapter for filesystem operations

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Principle

Implementation

Heuristic

Environment