cern.cpymad.madx

This module aims to provide the full functionality of the MAD-X library in a more convenient Python environment. For example, when you call the twiss method, you get numpy arrays containing the information from the table generated. Furthermore, we try to reduce the amount of commands needed by combining e.g. USE, SELECT, and TWISS into the twiss method itself, and define reasonable default patterns/columns etc. See, Madx example.

Module author: Yngve Inntjore Levinsen <Yngve.Inntjore.Levinsen.at.cern.ch>

Main module to interface with Mad-X library.

The class Madx uses a subprocess to execute MAD-X library calls remotely via a simple RPC protocol.

The remote backend is needed due to the fact that cpymad.libmadx is a low level binding to the MAD-X library which in turn uses global variables. This means that the cpymad.libmadx module has to be loaded within remote processes in order to deal with several isolated instances of MAD-X in parallel.

Furthermore, this can be used as a security enhancement: if dealing with unverified input, we can’t be sure that a faulty MAD-X function implementation will give access to a secure resource. This can be executing all library calls within a subprocess that does not inherit any handles.

More importantly: the MAD-X program crashes on the tinyest error. Boxing it in a subprocess will prevent the main process from crashing as well.

class cern.cpymad.madx.ChangeDirectory(path, _os=<module 'os' from '/usr/lib/python3.4/os.py'>)

Context manager for temporarily changing current working directory.

class cern.cpymad.madx.Madx(histfile=None, libmadx=None, logger=None)

Python class which interfaces to Mad-X library

active_sequence

Get/set the name of the active sequence.

aperture(sequence=None, pattern=['full'], madrange='', columns=['name', 'l', 'anglex', 'y', 'z', 'theta'], offsets=None, fname=None, use=False)

Run SELECT+USE+APERTURE.

Parameters:

• sequence (str) – name of sequence
• fname (str) – name of file to store tfs table
• pattern (list) – pattern to include in table
• columns (list) – columns to include in table (may be a str)
• use (bool) – Call use before aperture.

call(filename, chdir=False)

CALL a file in the MAD-X interpretor.

Parameters:

• filename (str) – file name with path
• chdir (bool) – temporarily change directory in MAD-X process

chdir(path)

Change the directory. Can be used as context manager.

Parameters:path (str) – new path name Returns:a context manager that can change the directory back Return type:ChangeDirectory

command

Perform a single MAD-X command.

Parameters:

• cmd (str) – command name
• **kwargs –

  command parameters

evaluate(cmd)

Evaluates an expression and returns the result as double.

Parameters:cmd (string) – expression to evaluate. Returns:numeric value of the expression Return type:float

get_active_sequence()

Get a handle to the active sequence.

Returns:a proxy object for the sequence Return type:Sequence Raises RuntimeError:  if there is no active sequence

get_sequence(name)

Get a handle to the specified sequence.

Parameters:name (str) – sequence name Returns:a proxy object for the sequence Return type:Sequence Raises ValueError:  if a sequence name is invalid

get_sequence_names()

Return list of all sequences currently in memory.

Returns:list of all sequences names Return type:list(str)

get_sequences()

Return list of all sequences currently in memory.

Returns:list of sequence proxy objects Return type:list(Sequence)

get_table(table)

Get the specified table columns as numpy arrays.

Parameters:

• table (str) – table name
• columns (list or str (comma separated)) – column names

help(cmd=None)

Show help about a command or list all MAD-X commands.

Parameters:cmd (str) – command name

input(text)

Run any textual MAD-X input.

Parameters:text (str) – command text

match(sequence, constraints, vary, weight=None, method=('lmdif', {}), fname=None, twiss_init={}, **kwargs)

Perform simple MATCH operation.

Parameters:

• sequence (string) – name of sequence
• constraints (list) – constraints to pose during matching
• vary (list) – vary commands
• weight (dict) – weights for matching parameters

select(flag, columns, pattern=[])

Run SELECT command.

Parameters:

• flag (str) – one of: twiss, makethin, error, seqedit
• columns (list) – column names
• pattern (list) – selected patterns

survey(sequence=None, pattern=['full'], columns=['name', 'l', 's', 'angle', 'x', 'y', 'z', 'theta'], madrange=None, fname=None, use=True)

Run SELECT+USE+SURVEY.

Parameters:

• sequence (str) – name of sequence
• fname (str) – name of file to store tfs table
• pattern (list) – pattern to include in table
• columns (list) – Columns to include in table
• use (bool) – Call use before survey.

twiss(sequence=None, pattern=['full'], columns=['name', 's', 'betx', 'bety', 'x', 'y', 'dx', 'dy', 'px', 'py', 'mux', 'muyl', 'k1l', 'angle', 'k2l'], madrange=None, fname=None, twiss_init={}, use=True, **kwargs)

Run SELECT+USE+TWISS.

Parameters:

• sequence (str) – name of sequence
• fname (str) – name of file to store tfs table
• pattern (list) – pattern to include in table
• columns (list) – columns to include in table, (may be a str)
• twiss_init (dict) – dictionary of twiss initialization variables
• use (bool) – Call use before aperture.
• chrom (bool) – Also calculate chromatic functions (slower)
• **kwargs –

  further keyword arguments to TWISS (betx, bety, ..).

Note, that the kwargs overwrite any arguments in twiss_init.

class cern.cpymad.madx.MadxCommands(dispatch)

Generic MAD-X command wrapper.

Raw python interface to issue MAD-X commands. Usage example:

>>> command = MadxCommands(libmadx.input)
>>> command('twiss', sequence='LEBT')
>>> command.title('A meaningful phrase')

Variables:__dispatch – callable that takes a MAD-X command string.

class cern.cpymad.madx.Sequence(name, libmadx, _check=True)

MAD-X sequence representation.

beam

Get the beam dictionary associated to the sequence.

get_elements()

Get list of all elements in the original sequence.

Returns:list of elements in the original (unexpanded) sequence Return type:list(Element)

get_expanded_elements()

Get list of all elements in the expanded sequence.

Returns:list of elements in the expanded (unexpanded) sequence Return type:list(Element)

NOTE: this may very well return an empty list, if the sequence has not been expanded (used) yet.

name

Get the name of the sequence.

twiss

Get the TWISS results from the last calculation.

twissname

Get the name of the table with the TWISS results.

class cern.cpymad.madx.Table(name, libmadx, _check=True)

MAD-X table access class.

columns

Get a lazy accessor for the table columns.

name

Get the table name.

summary

Get the table summary.

class cern.cpymad.madx.TableColumns(table, libmadx)

Lazy accessor for table column data.

freeze(columns=None)

Return a frozen table with the desired columns.

Parameters:columns (list) – column names or None for all columns. Returns:column data Return type:TfsTable Raises ValueError:  if the table name is invalid