otp.string

class string

Bases: str

OneTick data type representing string with length and varstring. To set string length use __getitem__. If the length is not set then the DEFAULT_LENGTH length is used by default. In this case using otp.string is the same as using str. If the length is set to Ellipse it represents varstring. Varstring is used for returning variably sized strings.

Note

If you try to set value with length x to string[y] and x > y, value will be truncated to y length.

Examples

Adding new fields with otp.string type:

>>> t = otp.Tick(A=otp.string[32]('HELLO'))
>>> t['B'] = otp.string[128]('WORLD')
>>> t.schema
{'A': string[32], 'B': string[128]}
>>> otp.run(t)
        Time      A      B
0 2003-12-01  HELLO  WORLD

Note that class otp.string is a child of python’s str class, so every object passed to constructor is converted to string. So it may not work as expected in some cases, e.g. when passing Operation objects (because their string representation is the name of the column or OneTick expression). In this case it’s better to use direct type conversion to get otp.string object:

>>> t = otp.Tick(X=otp.string[256](t['_SYMBOL_NAME']))
>>> t['Y'] = t['_SYMBOL_NAME'].astype(otp.string[256])
>>> t.schema
{'X': string[256], 'Y': string[256]}
>>> otp.run(t, symbols='AAAA')
        Time             X     Y
0 2003-12-01  _SYMBOL_NAME  AAAA

Setting the type of the existing field:

>>> t = otp.Tick(A='a')
>>> t = t.table(A=otp.string[10])
>>> t.schema
{'A': string[10]}

Example of truncation column value to set string length.

>>> t['A'] *= 100
>>> t['B'] = t['A'].str.len()
>>> otp.run(t)
        Time           A   B
0 2003-12-01  aaaaaaaaaa  10

Example of string with default length.

>>> t = otp.Tick(A='a')
>>> t['A'] *= 100
>>> t['B'] = t['A'].str.len()
>>> otp.run(t)
        Time                                                                 A   B
0 2003-12-01  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa  64

Setting Ellipsis as length represents varstring.

>>> t = otp.Tick(A='a')
>>> t = t.table(A=otp.string[...])
>>> t.schema
{'A': varstring}

Varstring length is multiplied.

>>> t['A'] *= 65
>>> t['B'] = t['A'].str.len()
>>> otp.run(t)
        Time                                                                  A   B
0 2003-12-01  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa  65

otp.varstring is a shortcut:

>>> t = otp.Tick(A='a')
>>> t = t.table(A=otp.varstring)
>>> t.schema
{'A': varstring}

Variables

DEFAULT_LENGTH (int) – default length of the string when the length is not specified

DEFAULT_LENGTH = 64