This command installs Python packages

pip install -r requirements.txt

How to make sure that it will install the correct versions of the packages?
The best way to make sure that pip installs the correct versions of the packages is to check the contents of requirements.txt. The command pip install -r requirements.txt will install the packages and versions listed in the file, so everything is dependent on that file being correct.
Thanks, but how do I make requirements.txt install certain versions for me? How can I make sure that it installs an exact version or a version that is at least > 2.0.3 for instance?
To install the exact version of a package, in your requirements.txt, specify the version

requirements.txt
```
package_name==2.0.3
```

To install a version > 2.03
```
package_name==2.0.3
```

The comparison operator determines the kind of version clause:
~=: Compatible release clause
==: Version matching clause
!=: Version exclusion clause
<=, >=: Inclusive ordered comparison clause
<, >: Exclusive ordered comparison clause
===: Arbitrary equality clause.
The comma (,) is equivalent to a logical and operator: a candidate version must match all given version clauses in order to match the specifier as a whole.