Tecplot ASCII#

.tec .dat read + write eager

Summary of the specification#

A Tecplot ASCII data file opens with an optional TITLE and a VARIABLES list naming every column, then one or more ZONE records. A finite-element zone declares its node and element counts (N=, E=), its element shape (ZONETYPE=FETRIANGLE, FEQUADRILATERAL, FETETRAHEDRON, FEBRICK) and its data packing. DATAPACKING=POINT interleaves all variables per node; DATAPACKING=BLOCK writes each variable’s full column in turn. The connectivity list follows the nodal data.

Specification at a glance#

header	TITLE = “…” then VARIABLES = “X” “Y” “Z” …
zone record	ZONE T=”name”, N=…, E=…, ZONETYPE=…, DATAPACKING=…
zone types	FETRIANGLE, FEQUADRILATERAL, FETETRAHEDRON, FEBRICK
packing	POINT (per node) or BLOCK (per variable)
connectivity	1-based node indices, one element per line
other suffixes	.dat resolves by content; .plt is binary and not read

Read the full Tecplot ASCII specification ↗

Reading#

import polyxios as px

mesh = px.read("model.tec")
mesh.vertices          # (n, 3)
mesh.element_types     # element groups found in the file

Writing#

px.write(mesh, "out.tec")

This codec takes no format-specific options.

Quirks worth knowing#

Both POINT and BLOCK packing are read; finite-element zones are supported, ordered (structured) zones are not.
Variables beyond the coordinate columns are read as named vertex attributes, so solution fields survive the round trip.
A zone declaring only X and Y is 2-D: the vertices are padded with a zero z and global_attrs["was_2d"] records the fact, which is what writes the zone back out with two coordinate variables rather than three. Tecplot names the coordinates by position, so a mesh carrying a variable of its own named Z keeps three: the zone would otherwise read back with that variable as its z. A mesh whose vertices have since left the plane is written in three with a warning, and a flat mesh of TETRAHEDRON or BRICK cells keeps three coordinate variables whatever the flag says - Tecplot takes the node count per element from ET and the coordinate count from VARIABLES, and the two have to agree.
.dat is shared with Nastran, LS-DYNA and plain ASCII tables, so it is resolved by looking inside the file: a .dat opening with TITLE = ", VARIABLES =, ZONE, FILETYPE = or DATASETAUXDATA lands here. An unquoted TITLE = decides nothing - Nastran case control spells its title the same way - so the line under it settles the question. px.read("flow.dat", fmt=".tec") still forces the issue, and writing to .dat needs fmt=".tec" because an output file has no content to inspect.
A variable that is not finite throughout is not written. The format spells no missing value, so a NaN - which is what a field covering part of a mesh carries over the rest of it - would go out as the token nan, and a zone holding one is a zone no reader loads.
Binary Tecplot (.plt) is registered so it fails with a clear message rather than not resolving at all; only the ASCII flavour is parsed.