StringFunctions
alias · alias_list · head · is_artificial · is_name · is_point_process · left · len · references · right · substr · tail

StringFunctions (String Manipulation Class)

class StringFunctions
Syntax:

sf = n.StringFunctions()

Description:

The StringFunctions class contains functions which you can apply to a strdef. This class exists purely for the utility of preventing pollution of name space with string operations.

Example:

from neuron import n
sf = n.StringFunctions()
Syntax:

obj = new StringFunctions()

Description:

The StringFunctions class contains functions which you can apply to a strdef. This class exists purely for the utility of preventing pollution of name space with string operations.

Example:

objref strobj
strobj = new StringFunctions()
StringFunctions.len()
Syntax:

length = sf.len(str)

Description:

Return the length of a string. Works with both NEURON string references and regular Python strings.

Example:
from neuron import n
sf = n.StringFunctions()
length = sf.len("hello")
print(length)

Note

This is approximately equivalent to len(s) for Python strings and to len(s[0]) for references to NEURON strings, but it uses the same syntax for both types of strings.

Syntax:

length = strobj.len(str)

Description:

Return the length of a string.

StringFunctions.substr()
Syntax:

index = sf.substr(s1, s2)

Description:

Return the index into s1 of the first occurrence of s2. If s2 isn’t a substring then the return value is -1. The arguments can be either NEURON string references or regular Python strings.

Example:
from neuron import n
s1 = n.ref("allowed")
s2 = n.ref("low")
sf = n.StringFunctions()
index = sf.substr(s1, s2)

Note

When working with pure Python strings (not NEURON string references), the return value is the same as s1.find(s2). e.g., sf.substr("allowed", "low") is equivalent to "allowed".find("low") and both return 2.

Syntax:

index = strobj.substr(s1, s2)

Description:

Return the index into s1 of the first occurrence of s2. If s2 isn’t a substring then the return value is -1.

StringFunctions.head()
Syntax:

sf.head(str, "regexp", result)

Description:

The result contains the head of the string up to but not including the regexp. returns index of last char.

Example:
from neuron import n
s1 = n.ref("hello world")
s2 = n.ref("")
sf = n.StringFunctions()
index = sf.head(s1, "[e]", s2)
print(s2[0])

See also

Python’s regular expression module re.

Syntax:

strobj.head(str, "regexp", result)

Description:

The result contains the head of the string up to but not including the regexp. returns index of last char.

StringFunctions.tail()
Syntax:

sf.tail(str, "regexp", result)

Description:

The result contains the tail of the string from the char following regexp to the end of the string. return index of first char.

Other functions can be added as needed, e.g., index(s1, c1), char(s1, i), etc. without polluting the global name space. In recent versions functions can return strings.

Example:
from neuron import n
s1 = n.ref("hello world")
s2 = n.ref("")
sf = n.StringFunctions()
index = sf.tail(s1, "[e]", s2)
print(s2[0])
Syntax:

strobj.tail(str, "regexp", result)

Description:

The result contains the tail of the string from the char following regexp to the end of the string. return index of first char.

Other functions can be added as needed, eg., index(s1, c1), char(s1, i), etc. without polluting the global name space. In recent versions functions can return strings.

StringFunctions.right()
Syntax:

sf.right(str, n)

Description:

Removes first n characters from the NEURON string str and puts the result back in str. This cannot be used with regular Python strings because they are immutable.

Example:
from neuron import n
s = n.ref("hello")
sf = n.StringFunctions()
sf.right(s, 3)
print(s[0])  # prints: "lo"

Note

This is approximately equivalent to s = s[n:] for Python strings except that it modifies the NEURON string in place. That is, sf.right(s, 3) always changes the value of s, while s = s[n:] creates a new string and assigns it to s, but it could be assigned to any other variable and leave the original string unchanged.

Syntax:

strobj.right(str, n)

Description:

Removes first n characters from str and puts the result in str.

StringFunctions.left()
Syntax:

sf.left(str, n)

Description:

Removes all but the first n characters from the NEURON string str and puts the result back in str. This cannot be used with regular Python strings because they are immutable.

Example:
from neuron import n
s = n.ref("hello")
sf = n.StringFunctions()
sf.left(s, 3)
print(s[0])  # prints "hel"

Note

This is approximately equivalent to s = s[:n] for Python strings except that it modifies the NEURON string in place. That is, sf.left(s, 3) always changes the value of s, while s = s[:n] creates a new string and assigns it to s, but it could be assigned to any other variable and leave the original string unchanged.

Syntax:

.left(str, n)

Description:

Removes all but first n characters from str and puts the result in str

StringFunctions.is_name()
Syntax:

sf.is_name(item)

Description:

Returns True if the item is the name of a symbol, False otherwise. This is so useful that the same thing is available with the top level name_declared() function (except that returns 1 or 0 instead of True or False).

Example:
from neuron import n
s1 = n.ref("hello world")
sf = n.StringFunctions()
name = sf.is_name(s1)
print(name)

Here is an example with one string that works, and another that does not:

from neuron import n
sf = n.StringFunctions()
# valid name
print(sf.is_name("xvalue"))
# invalid name
print(sf.is_name("xsquiggle"))

Note

This is approximately equivalent to item in dir(h) but the Python module h contains additional names that are not NEURON symbols per se.

Syntax:

.is_name(str)

Description:

Returns 1 if the str is the name of a symbol, 0 otherwise. This is so useful that the same thing is available with the top level name_declared() function.

StringFunctions.alias()
Syntax:

sf.alias(obj, "name", _ref_var2)

sf.alias(obj, "name", obj2)

sf.alias(obj, "name")

sf.alias(obj)

Description:

“name” becomes a public variable for obj and points to the scalar pointed at by _ref_var2 or object obj2. obj.name may be used anywhere the var2 or obj2 may be used. With no third arg, the “name” is removed from the objects alias list. With no second arg, the objects alias list is cleared.

Example:
from neuron import n
sf = n.StringFunctions()
v = n.Vector()
sf.alias(v, 't', n._ref_t)
print(f'v.t = {v.t}')
n.t = 42
print(f'v.t = {v.t}')
Syntax:

.alias(obj, "name", &var2)

.alias(obj, "name", obj2)

.alias(obj, "name")

.alias(obj)

Description:

“name” becomes a public variable for obj and points to the scalar var2 or object obj2. obj.name may be used anywhere the var2 or obj2 may be used. With no third arg, the “name” is removed from the objects alias list. With no second arg, the objects alias list is cleared.

StringFunctions.alias_list()
Syntax:

listobj = sf.alias_list(obj)

Description:

Return a new List object containing String objects which contain the alias names.

Warning

The String class is not a built-in class. It generally gets declared when gui is imported or stdrun.hoc is loaded. Note that the String class must exist and its constructor must allow a single strdef argument. Minimally:

Example:
from neuron import n
n.load_file('stdrun.hoc')
sf = n.StringFunctions()
v = n.Vector()
al = sf.alias_list(v)
print(al)
Syntax:

list = sf.alias_list(obj)

Description:

Return a new List object containing String objects which contain the alias names.

Warning

The String class is not a built-in class. It generally gets declared when the nrngui.hoc file is loaded and lives in stdlib.hoc. Note that the String class must exist and its constructor must allow a single strdef argument. Minimally:

begintemplate String
public s
strdef s
proc init() { s = $s1 }
endtemplate String
StringFunctions.references()
Syntax:

sf.references(object)

Description:

Prints the number of references to the object and all objref names that reference that object (including references via HBox, VBox, and List). It also prints the number of references found.

Example:
from neuron import n
soma = n.Section('soma')
sf = n.StringFunctions()
sf.references(soma)
Syntax:

sf.references(object)

Description:

Prints the number of references to the object and all objref names that reference that object (including references via HBox, VBox, and List). It also prints the number of references found.

StringFunctions.is_point_process()
Syntax:

i = sf.is_point_process(object)

Description:

Returns 0 if the object is not a POINT_PROCESS. Otherwise returns the point type (which is always 1 greater than the index into the MechanismType(1) list). In particular, the return value is an integer, not a boolean, because it indicates position in a list.

Example:
from neuron import n
n.load_file('stdrun.hoc')
s1 = n.Section('soma')
syn = n.ExpSyn(s1(0.5))
sf = n.StringFunctions()
# not point process
print(sf.is_point_process(s1))
# point process
print(sf.is_point_process(syn))
c = n.IntFire1()
# point process
print(ssf.is_point_process(c))
Syntax:

i = sf.is_point_process(object)

Description:

Returns 0 if the object is not a POINT_PROCESS. Otherwise returns the point type (which is always 1 greater than the index into the MechanismType(1) list).

StringFunctions.is_artificial()
Syntax:

i = sf.is_artificial(object)

Description:

Returns 0 if the object is not an ARTIFICIAL_CELL. Otherwise returns the point type (which is always 1 greater than the index into the MechanismType(1) list). In particular, the return value is an integer, not a boolean, because it indicates position in a list.

Example:
from neuron import n
n.load_file('stdrun.hoc')
s1 = n.Section('soma')
syn = n.ExpSyn(s1(0.5))
# initiate string function
sf = n.StringFunctions()
c = n.IntFire1()
# artificial
print(sf.is_artificial(c))
# not artificial
print(sf.is_artificial(syn))
Syntax:

i = sf.is_artificial(object)

Description:

Returns 0 if the object is not an ARTIFICIAL_CELL. Otherwise returns the point type (which is always 1 greater than the index into the MechanismType(1) list).