An innovative way to run Tcl and Python together — without wrappers or subprocess hacks

Combining Tcl and Python in a single workflow has traditionally been difficult. Most approaches rely on subprocess calls, file-based communication, or external wrappers — all of which introduce complexity, performance overhead, and synchronization issues. In many cases, users are forced to manually copy variable values between Tcl and Python contexts, which is error-prone and hard to maintain in complex scripts.

tclpysh offers a different solution: it allows Tcl and Python code to run natively in the same shell environment, with real-time variable sharing between the two languages.

1. Unified scripting: Tcl + Python in one file

tclpysh supports writing Tcl and Python code in the same script. Each language block is parsed and executed natively, without launching subprocesses or using glue code.

Mixed Language Script Example:

#!/edatool/tclpysh_py39_v2025.06/bin/tclpysh 

set a 0 
pymode 
print(f'python: a = {a}') 
b='1' 
tclmode() 
puts "tcl: a = $a" 
puts "tcl: b = $b" 
exit 

Interactive Command Line Example:

%  tclpysh 
tcl> set a 0 
0 
tcl> pymode 
py> a 
'0' 
py> b='1' 
py> tclmode() 
tcl> return $a 
0 
tcl> return $b 
1 
tcl> exit 
Info: thank you for using FusionShell! (err:0, crit:0, warn:0, info:1)

2. Third-party tool integration

tclpysh can be imported as a Python module into any tool that supports Python scripting. It runs an interactive Tcl+Python shell inside the host environment.

>>> import sys 
>>> sys.path = ['/edatool/tclpysh_py36_v2025.06/lib'] + sys.path 
>>> import tclpysh 
tcl> set a 0 
0 
tcl> pymode 
py> a 
'0' 
py> b='1' 
py> tclmode() 
tcl> return $a 
0 
tcl> return $b 
1 
tcl> exit

3. Enhanced shell behavior

tclpysh introduces several shell usability improvements over the standard tclsh:

Improved Ctrl-C: Can interrupt loops, conditionals, and procedures — not just top-level commands.

tcl> while 1 { incr i } 
^C 
Info: Ctrl-C interrupt: 'while 1 { incr i }'. (SHELL-INTRCMD) 
tcl> puts $i 
937237 

Smart Tab-completion: Supports commands, arguments, file paths, nested structures, and even user-defined procs.

tcl> string tr<tab> 
tcl> string trim<tab> 
trim  trimleft  trimright 
tcl> puts [string tr<tab> 
tcl> puts [string trim<tab> 
trim  trimleft  trimright 

Modern proc definitions: Supports argument parsing, type checking, default values, and help descriptions.

proc print {args} { 
   parse_proc_args -to_vars 
   puts ${-string} 
   puts ${-int} 
   puts $bool 
} 

define_proc_constraints print \ 
   -info "puts all arguments" \ 
   -default_arg {names=bool} \ 
   -switch_arg "name=string type=string optional=false" \ 
   -switch_arg "name=int type=int default=1"

These enhancements make scripting more robust and user-friendly — especially for long-running EDA tasks.

Who Benefits from tclpysh?

• CAD Teams Import tclpysh into Python-capable tools to enable hybrid Tcl/Python scripting, enhancing tool flexibility without changing existing interfaces.

• Script Developers Without launching an external Python environment, access thousands of open-source Python libraries within the familiar Tcl command-line for data processing, analysis, and customized EDA automation.

•Design Engineers Traditional Tcl users can boost productivity with tclpysh enhancements like interrupt handling, command completion, and advanced procedure customization.

Learn More:

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Online Playground:

https://dashthru.com/playground