Welcome, fellow programmer!
frozendict is a simple immutable dictionary. It's fast as dict, and
sometime faster!
Unlike other similar implementations, immutability is guaranteed: you can't
change the internal variables of the class, and they are all immutable
objects. Reinvoking __init__ does not alter the object.
The API is the same as dict, without methods that can change the
immutability. So it supports also fromkeys, unlike other implementations.
Furthermore it can be pickled, unpickled and have an hash, if all values
are hashable.
You can also add any dict to a frozendict using the | operator. The result is a new frozendict.
from frozendict import frozendict
fd = frozendict({"Sulla": "Marco", "Hicks": "Bill"})
print(fd)
# frozendict({'Sulla': 'Marco', 'Hicks': 'Bill'})
print(fd["Sulla"])
# Marco
fd["God"]
# KeyError: 'God'
len(fd)
# 2
"Sulla" in fd
# True
"Sulla" not in fd
# False
"God" in fd
# False
hash(fd)
# 5833699487320513741
fd_unhashable = frozendict({1: []})
hash(fd_unhashable)
# TypeError: Not all values are hashable.
fd | {1: 2}
# frozendict({'Sulla': 'Marco', 'Hicks': 'Bill', 1: 2})
fd5 = frozendict(fd)
id_fd5 = id(fd5)
fd5 |= {1: 2}
fd5
# frozendict.frozendict({'Sulla': 'Marco', 'Hicks': 'Bill', 1: 2})
id(fd5) != id_fd5
# True
fd2 = fd.copy()
fd2 == fd
# True
fd3 = frozendict(fd)
fd3 == fd
# True
fd4 = frozendict({"Hicks": "Bill", "Sulla": "Marco"})
print(fd4)
# frozendict({'Hicks': 'Bill', 'Sulla': 'Marco'})
fd4 == fd
# True
import pickle
fd_unpickled = pickle.loads(pickle.dumps(fd))
print(fd_unpickled)
# frozendict({'Sulla': 'Marco', 'Hicks': 'Bill'})
fd_unpickled == fd
# True
frozendict(Sulla="Marco", Hicks="Bill")
# frozendict({'Sulla': 'Marco', 'Hicks': 'Bill'}
frozendict((("Sulla", "Marco"), ("Hicks", "Bill")))
# frozendict({'Sulla': 'Marco', 'Hicks': 'Bill'})
fd.get("Sulla")
# 'Marco'
print(fd.get("God"))
# None
tuple(fd.keys())
# ('Sulla', 'Hicks')
tuple(fd.values())
# ('Marco', 'Bill')
tuple(fd.items())
# (('Sulla', 'Marco'), ('Hicks', 'Bill'))
frozendict.fromkeys(["Marco", "Giulia"], "Sulla")
# frozendict({'Marco': 'Sulla', 'Giulia': 'Sulla'})
iter(fd)
# <dict_keyiterator object at 0x7feb75c49188>
fd["Sulla"] = "Silla"
# TypeError: 'frozendict' object doesn't support item assignmentYou can build frozendict directly from the code, using
python3 setup.py bdist_wheel
The C Extension is not optional by default. You can build the pure py package using the py custom argument:
python3 setup.py py bdist_wheel
Some benchmarks between dict and coold, a C-only extended and experimental version of frozendict[1]:
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(d)`; Size: 5; Keys: str; Type: dict; Time: 8.02e-08; Sigma: 4e-09
Name: `constructor(d)`; Size: 5; Keys: str; Type: coold; Time: 8.81e-08; Sigma: 3e-09
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(d)`; Size: 5; Keys: int; Type: dict; Time: 7.96e-08; Sigma: 5e-09
Name: `constructor(d)`; Size: 5; Keys: int; Type: coold; Time: 8.97e-08; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(d)`; Size: 1000; Keys: str; Type: dict; Time: 6.38e-06; Sigma: 9e-08
Name: `constructor(d)`; Size: 1000; Keys: str; Type: coold; Time: 6.21e-06; Sigma: 2e-07
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(d)`; Size: 1000; Keys: int; Type: dict; Time: 3.49e-06; Sigma: 3e-07
Name: `constructor(d)`; Size: 1000; Keys: int; Type: coold; Time: 3.48e-06; Sigma: 2e-07
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(kwargs)`; Size: 5; Keys: str; Type: dict; Time: 2.40e-07; Sigma: 1e-09
Name: `constructor(kwargs)`; Size: 5; Keys: str; Type: coold; Time: 2.48e-07; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(kwargs)`; Size: 1000; Keys: str; Type: dict; Time: 4.80e-05; Sigma: 1e-06
Name: `constructor(kwargs)`; Size: 1000; Keys: str; Type: coold; Time: 2.90e-05; Sigma: 7e-07
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(seq2)`; Size: 5; Keys: str; Type: dict; Time: 2.01e-07; Sigma: 9e-10
Name: `constructor(seq2)`; Size: 5; Keys: str; Type: coold; Time: 2.50e-07; Sigma: 1e-09
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(seq2)`; Size: 5; Keys: int; Type: dict; Time: 2.18e-07; Sigma: 2e-09
Name: `constructor(seq2)`; Size: 5; Keys: int; Type: coold; Time: 2.73e-07; Sigma: 1e-09
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(seq2)`; Size: 1000; Keys: str; Type: dict; Time: 4.29e-05; Sigma: 6e-07
Name: `constructor(seq2)`; Size: 1000; Keys: str; Type: coold; Time: 4.33e-05; Sigma: 6e-07
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(seq2)`; Size: 1000; Keys: int; Type: dict; Time: 3.04e-05; Sigma: 4e-07
Name: `constructor(seq2)`; Size: 1000; Keys: int; Type: coold; Time: 3.45e-05; Sigma: 4e-07
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(o)`; Size: 5; Keys: str; Type: dict; Time: 7.93e-08; Sigma: 3e-09
Name: `constructor(o)`; Size: 5; Keys: str; Type: coold; Time: 2.41e-08; Sigma: 6e-10
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(o)`; Size: 5; Keys: int; Type: dict; Time: 7.94e-08; Sigma: 5e-09
Name: `constructor(o)`; Size: 5; Keys: int; Type: coold; Time: 2.41e-08; Sigma: 6e-10
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(o)`; Size: 1000; Keys: str; Type: dict; Time: 6.18e-06; Sigma: 3e-07
Name: `constructor(o)`; Size: 1000; Keys: str; Type: coold; Time: 2.41e-08; Sigma: 6e-10
////////////////////////////////////////////////////////////////////////////////
Name: `constructor(o)`; Size: 1000; Keys: int; Type: dict; Time: 3.47e-06; Sigma: 2e-07
Name: `constructor(o)`; Size: 1000; Keys: int; Type: coold; Time: 2.41e-08; Sigma: 6e-10
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `o.copy()`; Size: 5; Keys: str; Type: dict; Time: 7.28e-08; Sigma: 2e-09
Name: `o.copy()`; Size: 5; Keys: str; Type: coold; Time: 3.18e-08; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `o.copy()`; Size: 5; Keys: int; Type: dict; Time: 7.21e-08; Sigma: 4e-09
Name: `o.copy()`; Size: 5; Keys: int; Type: coold; Time: 3.32e-08; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `o.copy()`; Size: 1000; Keys: str; Type: dict; Time: 6.16e-06; Sigma: 3e-07
Name: `o.copy()`; Size: 1000; Keys: str; Type: coold; Time: 3.18e-08; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `o.copy()`; Size: 1000; Keys: int; Type: dict; Time: 3.46e-06; Sigma: 1e-07
Name: `o.copy()`; Size: 1000; Keys: int; Type: coold; Time: 3.18e-08; Sigma: 2e-09
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `o == o`; Size: 5; Keys: str; Type: dict; Time: 7.23e-08; Sigma: 8e-10
Name: `o == o`; Size: 5; Keys: str; Type: coold; Time: 2.44e-08; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `o == o`; Size: 5; Keys: int; Type: dict; Time: 7.30e-08; Sigma: 1e-09
Name: `o == o`; Size: 5; Keys: int; Type: coold; Time: 2.44e-08; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `o == o`; Size: 1000; Keys: str; Type: dict; Time: 1.38e-05; Sigma: 1e-07
Name: `o == o`; Size: 1000; Keys: str; Type: coold; Time: 2.44e-08; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `o == o`; Size: 1000; Keys: int; Type: dict; Time: 1.05e-05; Sigma: 7e-08
Name: `o == o`; Size: 1000; Keys: int; Type: coold; Time: 2.44e-08; Sigma: 2e-09
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o`; Size: 5; Keys: str; Type: dict; Time: 7.33e-08; Sigma: 2e-09
Name: `for x in o`; Size: 5; Keys: str; Type: coold; Time: 6.70e-08; Sigma: 1e-09
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o`; Size: 5; Keys: int; Type: dict; Time: 7.33e-08; Sigma: 2e-09
Name: `for x in o`; Size: 5; Keys: int; Type: coold; Time: 6.70e-08; Sigma: 1e-09
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o`; Size: 1000; Keys: str; Type: dict; Time: 8.84e-06; Sigma: 5e-08
Name: `for x in o`; Size: 1000; Keys: str; Type: coold; Time: 7.06e-06; Sigma: 6e-08
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o`; Size: 1000; Keys: int; Type: dict; Time: 8.67e-06; Sigma: 7e-08
Name: `for x in o`; Size: 1000; Keys: int; Type: coold; Time: 6.94e-06; Sigma: 3e-08
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o.values()`; Size: 5; Keys: str; Type: dict; Time: 7.28e-08; Sigma: 9e-10
Name: `for x in o.values()`; Size: 5; Keys: str; Type: coold; Time: 6.48e-08; Sigma: 8e-10
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o.values()`; Size: 5; Keys: int; Type: dict; Time: 7.25e-08; Sigma: 1e-09
Name: `for x in o.values()`; Size: 5; Keys: int; Type: coold; Time: 6.45e-08; Sigma: 1e-09
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o.values()`; Size: 1000; Keys: str; Type: dict; Time: 9.06e-06; Sigma: 5e-07
Name: `for x in o.values()`; Size: 1000; Keys: str; Type: coold; Time: 7.04e-06; Sigma: 4e-08
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o.values()`; Size: 1000; Keys: int; Type: dict; Time: 9.53e-06; Sigma: 3e-08
Name: `for x in o.values()`; Size: 1000; Keys: int; Type: coold; Time: 6.97e-06; Sigma: 3e-08
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o.items()`; Size: 5; Keys: str; Type: dict; Time: 1.13e-07; Sigma: 3e-09
Name: `for x in o.items()`; Size: 5; Keys: str; Type: coold; Time: 1.16e-07; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o.items()`; Size: 5; Keys: int; Type: dict; Time: 1.14e-07; Sigma: 3e-09
Name: `for x in o.items()`; Size: 5; Keys: int; Type: coold; Time: 1.17e-07; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o.items()`; Size: 1000; Keys: str; Type: dict; Time: 1.53e-05; Sigma: 3e-07
Name: `for x in o.items()`; Size: 1000; Keys: str; Type: coold; Time: 1.53e-05; Sigma: 4e-07
////////////////////////////////////////////////////////////////////////////////
Name: `for x in o.items()`; Size: 1000; Keys: int; Type: dict; Time: 1.53e-05; Sigma: 3e-07
Name: `for x in o.items()`; Size: 1000; Keys: int; Type: coold; Time: 1.55e-05; Sigma: 4e-07
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `pickle.dumps(o)`; Size: 5; Keys: str; Type: dict; Time: 6.82e-07; Sigma: 2e-08
Name: `pickle.dumps(o)`; Size: 5; Keys: str; Type: coold; Time: 2.86e-06; Sigma: 1e-07
////////////////////////////////////////////////////////////////////////////////
Name: `pickle.dumps(o)`; Size: 5; Keys: int; Type: dict; Time: 4.77e-07; Sigma: 2e-08
Name: `pickle.dumps(o)`; Size: 5; Keys: int; Type: coold; Time: 2.72e-06; Sigma: 8e-08
////////////////////////////////////////////////////////////////////////////////
Name: `pickle.dumps(o)`; Size: 1000; Keys: str; Type: dict; Time: 1.24e-04; Sigma: 4e-06
Name: `pickle.dumps(o)`; Size: 1000; Keys: str; Type: coold; Time: 1.92e-04; Sigma: 5e-06
////////////////////////////////////////////////////////////////////////////////
Name: `pickle.dumps(o)`; Size: 1000; Keys: int; Type: dict; Time: 2.81e-05; Sigma: 6e-07
Name: `pickle.dumps(o)`; Size: 1000; Keys: int; Type: coold; Time: 7.37e-05; Sigma: 1e-06
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `pickle.loads(dump)`; Size: 5; Keys: str; Type: dict; Time: 9.08e-07; Sigma: 6e-09
Name: `pickle.loads(dump)`; Size: 5; Keys: str; Type: coold; Time: 1.79e-06; Sigma: 9e-08
////////////////////////////////////////////////////////////////////////////////
Name: `pickle.loads(dump)`; Size: 5; Keys: int; Type: dict; Time: 4.46e-07; Sigma: 6e-09
Name: `pickle.loads(dump)`; Size: 5; Keys: int; Type: coold; Time: 1.32e-06; Sigma: 7e-08
////////////////////////////////////////////////////////////////////////////////
Name: `pickle.loads(dump)`; Size: 1000; Keys: str; Type: dict; Time: 1.57e-04; Sigma: 8e-06
Name: `pickle.loads(dump)`; Size: 1000; Keys: str; Type: coold; Time: 1.69e-04; Sigma: 7e-06
////////////////////////////////////////////////////////////////////////////////
Name: `pickle.loads(dump)`; Size: 1000; Keys: int; Type: dict; Time: 5.97e-05; Sigma: 5e-06
Name: `pickle.loads(dump)`; Size: 1000; Keys: int; Type: coold; Time: 6.68e-05; Sigma: 2e-06
################################################################################
////////////////////////////////////////////////////////////////////////////////
Name: `class.fromkeys()`; Size: 5; Keys: str; Type: dict; Time: 1.88e-07; Sigma: 1e-09
Name: `class.fromkeys()`; Size: 5; Keys: str; Type: coold; Time: 2.22e-07; Sigma: 7e-09
////////////////////////////////////////////////////////////////////////////////
Name: `class.fromkeys()`; Size: 5; Keys: int; Type: dict; Time: 2.08e-07; Sigma: 6e-09
Name: `class.fromkeys()`; Size: 5; Keys: int; Type: coold; Time: 2.44e-07; Sigma: 2e-09
////////////////////////////////////////////////////////////////////////////////
Name: `class.fromkeys()`; Size: 1000; Keys: str; Type: dict; Time: 4.05e-05; Sigma: 4e-06
Name: `class.fromkeys()`; Size: 1000; Keys: str; Type: coold; Time: 3.84e-05; Sigma: 5e-07
////////////////////////////////////////////////////////////////////////////////
Name: `class.fromkeys()`; Size: 1000; Keys: int; Type: dict; Time: 2.93e-05; Sigma: 7e-07
Name: `class.fromkeys()`; Size: 1000; Keys: int; Type: coold; Time: 3.08e-05; Sigma: 2e-06
################################################################################
[1] Benchmarks done under Linux 64 bit, Python 3.10.2, using the C Extension.