# Requirements File Format¶

Requirements files serve as a list of items to be installed by pip, when using pip install. Files that use this format are often called “pip requirements.txt files”, since requirements.txt is usually what these files are named (although, that is not a requirement).

Note

The requirements file format is closely tied to a number of internal details of pip (e.g., pip’s command line options). The basic format is relatively stable and portable but the full syntax, as described here, is only intended for consumption by pip, and other tools should take that into account before using it for their own purposes.

## Structure¶

Each line of the requirements file indicates something to be installed, or arguments to pip install. The following forms are supported:

• [[--option]...]

• <requirement specifier> [; markers] [[--option]...]

• <archive url/path>

• [-e] <local project path>

• [-e] <vcs project url>

For details on requirement specifiers, see Requirement Specifiers. For examples of all these forms, see Examples.

### Encoding¶

Requirements files are utf-8 encoding by default and also support PEP 263 style comments to change the encoding (i.e. # -*- coding: <encoding name> -*-).

### Line continuations¶

A line ending in an unescaped \ is treated as a line continuation and the newline following it is effectively ignored.

A line that begins with # is treated as a comment and ignored. Whitespace followed by a # causes the # and the remainder of the line to be treated as a comment.

Comments are stripped after line continuations are processed.

## Supported options¶

Requirements files only supports certain pip install options, which are listed below.

### Global options¶

The following options have an effect on the entire pip install run, and must be specified on their individual lines.

Example

To specify --pre, --no-index and two --find-links locations:

--pre
--no-index


### Per-requirement options¶

The options which can be applied to individual requirements are:

If you wish, you can refer to other requirements files, like this:

-r more_requirements.txt


You can also refer to constraints files, like this:

-c some_constraints.txt


## Using environment variables¶

New in version 10.0.

pip supports the use of environment variables inside the requirements file.

You have to use the POSIX format for variable names including brackets around the uppercase name as shown in this example: ${API_TOKEN}. pip will attempt to find the corresponding environment variable defined on the host system at runtime. Note There is no support for other variable expansion syntaxes such as $VARIABLE and %VARIABLE%.

You can now store sensitive data (tokens, keys, etc.) in environment variables and only specify the variable name for your requirements, letting pip lookup the value at runtime. This approach aligns with the commonly used 12-factor configuration pattern.

## Example¶

###### Requirements without Version Specifiers ######
pytest
pytest-cov
beautifulsoup4

###### Requirements with Version Specifiers ######
#   See https://www.python.org/dev/peps/pep-0440/#version-specifiers
docopt == 0.6.1             # Version Matching. Must be version 0.6.1
keyring >= 4.1.1            # Minimum version 4.1.1
coverage != 3.5             # Version Exclusion. Anything except version 3.5
Mopidy-Dirble ~= 1.1        # Compatible release. Same as >= 1.1, == 1.*

###### Refer to other requirements files ######
-r other-requirements.txt

###### A particular file ######