# ERROR: Invalid requirement: 'numpy>=1.19.0,<2.0'

- **ID:** `python/pip-invalid-requirement-package-name`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Pip cannot parse the requirement string due to incorrect syntax (e.g., missing quotes, extra spaces).

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.9 | active | — | — |

## Workarounds

1. **Use proper requirement format with quotes** (95% success)
   ```
   pip install 'numpy>=1.19.0,<2.0'
   ```
2. **Specify in requirements.txt correctly** (90% success)
   ```
   echo 'numpy>=1.19.0,<2.0' >> requirements.txt
pip install -r requirements.txt
   ```

## Dead Ends

- **Removing version specifiers entirely** — Loses version constraints; may install incompatible version. (70% fail)
- **Using semicolon instead of comma** — Pip uses commas for multiple constraints; semicolon is invalid. (90% fail)