We spend a fair amount of time organizing and counting wells when writing Python protocols. This section describes the different ways we can access wells and groups of wells.

Labware Library

The Opentrons API comes with many common labware built in. These can be loaded into your Python protocol by using the labware.load() method with the specific load name of the labware you need.

Please see the Opentrons Labware Library for a list of currently supported labware, along with visualizations, pictures, and load names.


Copy and paste load names directly from the Labware Library to ensure your load() statements get the correct definitions.

If you are interested in using your own labware that is not included in the API, please take a look at how to create custom labware definitions using labware.create(), or contact Opentrons Support.

Placing labware on the robot deck

The robot deck is made up of slots labeled 1, 2, 3, 4, and so on.


To tell the robot what labware will be on the deck for your protocol, use labware.load after importing labware as follows:

from opentrons import labware

# ...

tiprack = labware.load('opentrons_96_tiprack_300ul', slot='1')

Labware Import Reference

Examples in this section require the following
from opentrons import labware


labware.load tells the robot that your protocol will be using a given labware in a certain slot.

my_labware = labware.load('usascientific_12_reservoir_22ml', slot='1')

A third optional argument can be used to give a labware a nickname for display in the Opentrons App.

my_labware = labware.load('usascientific_12_reservoir_22ml',

Sometimes, you may need to place a labware on top of something else on the deck, like modules. For this, you should use the share parameter.

from opentrons import labware, modules

td = modules.load('tempdeck', slot='1')
plate = labware.load('opentrons_96_aluminumblock_biorad_wellplate_200ul',



The current custom labware creation mechanisms in the API are fairly limited. We’re working on a much more robust system for custom labware definitions. If the current API isn’t able to support your labware, please reach out to our support team.

Using labware.create, you can create your own custom labware. The labware created through this method must consist of circular wells arranged in regularly-spaced columns and rows.

custom_plate_name = 'custom_18_wellplate_200ul'

if plate_name not in labware.list():
        custom_plate_name,  # name of you labware
        grid=(3, 6),        # number of (columns, rows)
        spacing=(12, 12),   # distances (mm) between each (column, row)
        diameter=5,         # diameter (mm) of each well
        depth=10,           # depth (mm) of each well
        volume=200)         # volume (µL) of each well

custom_plate = labware.load(custom_plate_name, slot='3')

for well in custom_plate.wells():

The above example will print out...

<Well A1>
<Well B1>
<Well C1>
<Well A2>
<Well B2>
<Well C2>
<Well A3>
<Well B3>
<Well C3>
<Well A4>
<Well B4>
<Well C4>
<Well A5>
<Well B5>
<Well C5>
<Well A6>
<Well B6>
<Well C6>

You only need to call labware.create once. It will save the labware definition on the robot so that your labware will be available to all your subsequent protocol runs.

labware.create will throw an error if you try to call it more than once with the same load name. In the example above, the call to labware.create is wrapped in an if-block so it does not try to add the definition twice, which would cause an error.

If you would like to delete a labware you have already added to the database (for example: to make changes to its definition), you can do the following:

from opentrons.data_storage import database



There is some specialty labware that will require you to specify the type within your labware name. If you are creating a custom tip rack, it must be tiprack-REST-OF-LABWARE-NAME in order for the software to act reliably.

List (deprecated)

labware.list returns an array of all labware load names in the old, unsupported format.



For a list of all currently supported labware, please visit the Opentrons Labware Library

Accessing Wells

Individual Wells

When writing a protocol using the API, you will need to select which wells to transfer liquids to and from.

The OT-2 deck and labware are all set up with the same coordinate system

  • Lettered rows ['A']-['END']
  • Numbered columns ['1']-['END'].
Examples in this section expect the following
from opentrons import labware

plate = labware.load('corning_24_wellplate_3.4ml_flat', slot='1')

Wells by Name

Once a labware is loaded into your protocol, you can easily access the many wells within it using wells() method. wells() takes the name of the well as an argument, and will return the well at that location.

a1 = plate.wells('A1')
d6 = plate.wells('D6')

Wells by Index

Wells can be referenced by their “string” name, as demonstrated above. However, they can also be referenced with zero-indexing, with the first well in a labware being at position 0.

plate.wells(0)   # well A1
plate.wells(23)  # well D6


You may find well names (e.g. B3) to be easier to reason with, especially with irregular labware (e.g. opentrons_10_tuberack_falcon_4x50ml_6x15ml_conical). Whichever well access method you use, your protocol will be most maintainable if you pick one method and don’t use the other one.

Columns and Rows

A labware’s wells are organized within a series of columns and rows, which are also labelled on standard labware. In the API, rows are given letter names ('A' through 'D' for example) and go left to right, while columns are given numbered names ('1' through '6' for example) and go from front to back.

You can access a specific row or column by using the rows() and columns() methods on a labware. These will return all wells within that row or column.

row = plate.rows('A')
column = plate.columns('1')

print('Column "1" has', len(column), 'wells')
print('Row "A" has', len(row), 'wells')

will print out...

Column "1" has 4 wells
Row "A" has 6 wells

The rows() or cols() methods can be used in combination with the wells() method to access wells within that row or column. In the example below, both lines refer to well 'A1'.



The example above works but is a little convoluted. If you can, always get individual wells like A1 with wells('A1') or wells(0)

Multiple Wells

If we had to reference each well one at a time, our protocols could get very long.

When describing a liquid transfer, we can point to groups of wells for the liquid’s source and/or destination. Or, we can get a group of wells and loop (or iterate) through them.

Examples in this section expect the following
from opentrons import labware

plate = labware.load('corning_24_wellplate_3.4ml_flat', slot='1')


The wells() method can return a single well, or it can return a list of wells when multiple arguments are passed.

Here is an example or accessing a list of wells, each specified by name:

w = plate.wells('A1', 'B2', 'C3', 'D4')


will print out...

<WellSeries: <Well A1><Well B2><Well C3><Well D4>>

Multiple wells can be treated just like a normal Python list, and can be iterated through:

for w in plate.wells('A1', 'B2', 'C3', 'D4'):

will print out...

<Well A1>
<Well B2>
<Well C3>
<Well D3>

Wells To

Instead of having to list the name of every well, we can also create a range of wells with a start and end point. The first argument is the starting well, and the to= argument is the last well.

for w in plate.wells('A1', to='D1'):

will print out...

<Well A1>
<Well B1>
<Well C1>
<Well D1>

These lists of wells can also move in the reverse direction along your labware. For example, setting the to= argument to a well that comes before the starting position is allowed:

for w in plate.wells('D1', to='A1'):

will print out...

<Well D1>
<Well C1>
<Well B1>
<Well A1>

Wells Length

Another way you can create a list of wells is by specifying the length of the well list you need, including the starting well. The example below will return 4 wells, starting at well 'A1':

for w in plate.wells('A1', length=4):

will print out...

<Well A1>
<Well B1>
<Well C1>
<Well D1>

Columns and Rows

The same arguments described above can be used with rows() and cols() to create lists of rows or columns.

Here is an example of iterating through rows:

for r in plate.rows('A', length=3):

will print out...

<WellSeries: <Well A1><Well A2><Well A3><Well A4><Well A5><Well A6>>
<WellSeries: <Well B1><Well B2><Well B3><Well B4><Well B5><Well B6>>
<WellSeries: <Well C1><Well C2><Well C3><Well C4><Well C5><Well C6>>

And here is an example of iterating through columns:

for c in plate.cols('1', to='6'):

will print out...

<WellSeries: <Well A1><Well B1><Well C1><Well D1>>
<WellSeries: <Well A2><Well B2><Well C2><Well D2>>
<WellSeries: <Well A3><Well B3><Well C3><Well D3>>
<WellSeries: <Well A4><Well B4><Well C4><Well D4>>
<WellSeries: <Well A5><Well B5><Well C5><Well D5>>
<WellSeries: <Well A6><Well B6><Well C6><Well D6>>


Labware can also be treating similarly to Python lists, and can therefore handle slices.

# start at index 0
# slice until index 8, without including it
# increment by 2
for w in plate[0:8:2]:

will print out...

<Well A1>
<Well C1>
<Well A2>
<Well C2>

The API’s labware are also prepared to take string values for the slice’s start and stop positions.

for w in plate['A1':'A2':2]:

will print out...

<Well A1>
<Well C1>
for w in plate.rows['B']['1'::2]:

will print out...

<Well B1>
<Well B3>
<Well B5>

Deprecated Labware Load Names

Prior to version 3.10.0 of the Opentrons API, we used a completely different set of labware load names. They will continue to work until version 4.0.0 is released, but they should be considered deprecated.

We recommend you switch over to using the load names from the Labware Library as soon as possible. The following mapping can be used as a guide:

Deprecated Recommended Notes
6-well-plate corning_6_wellplate_16.8ml_flat  
12-well-plate corning_12_wellplate_6.9ml_flat  
24-well-plate corning_24_wellplate_3.4ml_flat  
48-well-plate corning_48_wellplate_1.6ml_flat  
384-plate corning_384_wellplate_112ul_flat  
96-deep-well usascientific_96_wellplate_2.4ml_deep This labware has square wells
96-flat corning_96_wellplate_360ul_flat  
96-PCR-flat biorad_96_wellplate_200ul_pcr  
96-PCR-tall biorad_96_wellplate_200ul_pcr  
alum-block-pcr-strips opentrons_40_aluminumblock_eppendorf_24x2ml_safelock_snapcap_generic_16x0.2ml_pcr_strip This product has been discontinued
biorad-hardshell-96-PCR biorad_96_wellplate_200ul_pcr  
opentrons-aluminum-block-2ml-eppendorf opentrons_24_aluminumblock_generic_2ml_screwcap Opentrons Aluminum Block Set
opentrons-aluminum-block-2ml-screwcap opentrons_24_aluminumblock_generic_2ml_screwcap Opentrons Aluminum Block Set
opentrons-aluminum-block-96-PCR-plate opentrons_96_aluminumblock_biorad_wellplate_200ul Opentrons Aluminum Block Set
opentrons-aluminum-block-PCR-strips-200ul opentrons_96_aluminumblock_generic_pcr_strip_200ul Opentrons Aluminum Block Set
opentrons-tiprack-300ul opentrons_96_tiprack_300ul  
opentrons-tuberack-1.5ml-eppendorf opentrons_24_tuberack_eppendorf_1.5ml_safelock_snapcap Opentrons 4-in-1 Tube Rack Set
opentrons-tuberack-15_50ml opentrons_10_tuberack_falcon_4x50ml_6x15ml_conical Opentrons 4-in-1 Tube Rack Set
opentrons-tuberack-15ml opentrons_15_tuberack_falcon_15ml_conical Opentrons 4-in-1 Tube Rack Set
opentrons-tuberack-2ml-eppendorf opentrons_24_tuberack_eppendorf_2ml_safelock_snapcap Opentrons 4-in-1 Tube Rack Set
opentrons-tuberack-2ml-screwcap opentrons_24_tuberack_generic_2ml_screwcap Opentrons 4-in-1 Tube Rack Set
opentrons-tuberack-50ml opentrons_6_tuberack_falcon_50ml_conical Opentrons 4-in-1 Tube Rack Set
PCR-strip-tall opentrons_96_aluminumblock_generic_pcr_strip_200ul  
tiprack-10ul opentrons_96_tiprack_10ul If possible, please use an Opentrons tip rack rather than a rack with a slot adapter
tiprack-200ul tipone_96_tiprack_200ul If possible, please use an Opentrons tip rack rather than a rack with a slot adapter
tiprack-1000ul opentrons_96_tiprack_1000ul If possible, please use an Opentrons tip rack rather than a rack with a slot adapter
trash-box agilent_1_reservoir_290ml trash-box is no longer supported; we recommend using a 1-well reservoir for liquid trash
trough-12row usascientific_12_reservoir_22ml  
tube-rack-.75ml opentrons_24_tuberack_generic_0.75ml_snapcap_acrylic Discontinued; please upgrade to the Opentrons 4-in-1 Tube Rack Set
tube-rack-2ml opentrons_24_tuberack_eppendorf_2ml_safelock_snapcap_acrylic Discontinued; please upgrade to the Opentrons 4-in-1 Tube Rack Set
tube-rack-15_50ml opentrons_10_tuberack_falcon_4x50ml_6x15ml_conical_acrylic Discontinued; please upgrade to the Opentrons 4-in-1 Tube Rack Set


If your labware is missing from the list above, or you’re unsure how to update your protocol’s load names, please contact our support team

The following load names do not have a new definitions available, and could eventually be removed. They will continue to function normally for now. If you have any concerns about their deprecation and/or removal, please reach out!

  • 24-vial-rack
  • 48-vial-plate
  • 5ml-3x4
  • 96-well-plate-20mm
  • MALDI-plate
  • T25-flask
  • T75-flask
  • e-gelgol
  • hampton-1ml-deep-block
  • point
  • rigaku-compact-crystallization-plate
  • small_vial_rack_16x45
  • temperature-plate
  • tiprack-10ul-H
  • trough-12row-short
  • trough-1row-25ml
  • trough-1row-test
  • tube-rack-2ml-9x9
  • tube-rack-5ml-96
  • tube-rack-80well
  • wheaton_vial_rack