To check if a path is a Directory in Python you can use the snippet below.
Sample Python
import os
print(os.path.isdir("/myfolder/folder1"))
or
How to check if String is Null or Empty in XSL
To check if String is Null or Empty in XSL you can use the following snippet.
Sample XSL
<xsl:choose>
<xsl:when test="fieldToTest != ''">
<xsl:value-of select="Field1Value" />
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="Field2Value" />
</xsl:otherwise>
</xsl:choose>