Get required fields from a given object. Code is supposed to execute as anonymous code in SF developer console

GetRequiredFields.apex

string objectName = 'Assessment__c';           // Usage: change the object name here
Map<String, Schema.SObjectType> gdesc = Schema.getGlobalDescribe();
Sobject objectt = gdesc.get(objectName).newSObject();
Schema.DescribeSObjectResult r = objectt.getSObjectType().getDescribe();
Map<String,Schema.SObjectField> M = r.fields.getMap();
for(String fieldName : M.keySet()) {
    Schema.SObjectField field = M.get(fieldName);
    Schema.DescribeFieldResult F = field.getDescribe();
    Boolean isFieldreq = F.isCreateable() && !F.isNillable() && !F.isDefaultedOnCreate();
    if (isFieldreq) {
        System.debug(fieldName);
    }
}