pypi-version-lookup

PyPI Version Lookup

Look up the latest published version of a Python package from the PyPI JSON API using curl and jq.

When to use this

• The user asks for the current/latest version of a Python package
• You need to pin or update a dependency version in any config file
• You're generating a requirements file and want accurate, up-to-date versions
• You want to verify whether a specific version exists

How it works

Query the PyPI JSON API for a package and extract the info.version field, which always reflects the latest stable release.

curl -sf --max-time 5 "https://pypi.org/pypi/<package>/json" | jq -r '.info.version'

Replace <package> with the exact PyPI package name (e.g., requests, numpy, flask).

Flags explained

• -s — Silent mode; suppresses progress output.
• -f — Fail silently on HTTP errors (returns a non-zero exit code instead of HTML error pages). This makes it easy to detect failures via $?.
• --max-time 5 — Abort if the entire request takes longer than 5 seconds.

Handling multiple packages

When looking up several packages at once, run the lookups in a loop:

for pkg in requests flask numpy; do
  version=$(curl -sf --max-time 5 "https://pypi.org/pypi/${pkg}/json" | jq -r '.info.version')
  if [ $? -eq 0 ] && [ -n "$version" ] && [ "$version" != "null" ]; then
    echo "${pkg}==${version}"
  else
    echo "${pkg}: lookup failed" >&2
  fi
done

Error handling and retries

Network blips happen. If a lookup fails (non-zero exit code, empty result, or the string "null"), retry up to 3 times with exponential backoff before giving up:

lookup_version() {
  local pkg="$1"
  local attempt=0
  local max_retries=3
  local version=""

  while [ $attempt -lt $max_retries ]; do
    version=$(curl -sf --max-time 5 "https://pypi.org/pypi/${pkg}/json" | jq -r '.info.version')
    if [ $? -eq 0 ] && [ -n "$version" ] && [ "$version" != "null" ]; then
      echo "$version"
      return 0
    fi
    attempt=$((attempt + 1))
    sleep $((2 ** attempt))  # 2s, 4s, 8s backoff
  done

  echo "Failed to fetch version for '${pkg}' after ${max_retries} attempts." >&2
  return 1
}