pypa/pip · error · InstallationError

Could not open file

Error message

Could not open {kind} file: {exc}

What it means

pip could not open the requirements file or constraint file specified with -r or -c. The get_file_content() function tried to open the path as a local file and caught an OSError (file not found, permission denied, or other I/O error). The error message distinguishes between 'requirements' and 'constraint' based on the constraint flag.

Solutions

1. Verify the file exists: 'ls -la requirements.txt'
2. Check for typos in the filename and path
3. Ensure the file is committed to version control for CI environments
4. Use absolute paths or verify the working directory: 'pwd' before running pip

import os

def requirements_file_exists(path: str) -> bool:
    return os.path.isfile(path) and os.access(path, os.R_OK)

if not requirements_file_exists("requirements.txt"):
    print("Requirements file not found or not readable — check path and permissions")

import os

def is_accessible_requirements_file(path: str) -> bool:
    """Type guard: True if path is a readable file."""
    return os.path.isfile(path) and os.access(path, os.R_OK)

from pip._internal.exceptions import InstallationError
from pip._internal.req.req_file import parse_requirements

try:
    list(parse_requirements("requirements.txt", session))
except InstallationError as e:
    if "Could not open" in str(e):
        print("Verify the filename, path, and working directory")
    else:
        raise

When it happens

Trigger: Running 'pip install -r requirements.txt' when requirements.txt does not exist. Using '-c constraints.txt' when the file is missing or unreadable. Any OSError from open() on a local requirements/constraint file path.

Common situations: Wrong filename or path. File not checked into version control so CI can't find it. Wrong working directory. Permission issues. File path with a typo or wrong extension.

Related errors

• Could not split options
• Error reading
• Error reading pylock file
• Invalid requirement
• not found. Cannot resolve '--group' option.

AI-assisted analysis of pypa/pip@f399c37189 (2026-08-08). Data as JSON: /api/errors/7a65899c14048cef. Report an issue: GitHub.

Appendix: source

Thrown at src/pip/_internal/req/req_file.py:589

    :param session:     PipSession instance.
    """
    scheme = urllib.parse.urlsplit(url).scheme
    # Pip has special support for file:// URLs (LocalFSAdapter).
    if scheme in ["http", "https", "file"]:
        # Delay importing heavy network modules until absolutely necessary.
        from pip._internal.network.utils import raise_for_status

        resp = session.get(url)
        raise_for_status(resp)
        return resp.url, resp.text

    # Assume this is a bare path.
    try:
        with open(url, "rb") as f:
            raw_content = f.read()
    except OSError as exc:
        kind = "constraint" if constraint else "requirements"
        raise InstallationError(f"Could not open {kind} file: {exc}")

    content = _decode_req_file(raw_content, url)

    return url, content


def _decode_req_file(data: bytes, url: str) -> str:
    for bom, encoding in BOMS:
        if data.startswith(bom):
            return data[len(bom) :].decode(encoding)

    for line in data.split(b"\n")[:2]:
        if line[0:1] == b"#":
            result = PEP263_ENCODING_RE.search(line)
            if result is not None:
                encoding = result.groups()[0].decode("ascii")
                return data.decode(encoding)

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