monty 0.0.20

A sandboxed, snapshotable Python interpreter written in Rust.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163

import itertools

# === count: basic progression ===
c = itertools.count()
assert [next(c) for _ in range(3)] == [0, 1, 2]
assert [next(itertools.count(10)) for _ in range(1)] == [10]
c2 = itertools.count(10, 2)
assert [next(c2) for _ in range(3)] == [10, 12, 14]
c3 = itertools.count(2, -1)
assert [next(c3) for _ in range(3)] == [2, 1, 0]
c4 = itertools.count(2.5, 0.5)
assert [next(c4) for _ in range(3)] == [2.5, 3.0, 3.5]

# start/step are accepted as keywords
assert [x for _, x in zip(range(2), itertools.count(start=5))] == [5, 6]
assert [x for _, x in zip(range(2), itertools.count(start=5, step=2))] == [5, 7]
assert [x for _, x in zip(range(2), itertools.count(step=3))] == [0, 3]
# bool is an int subclass, so it counts as a number — and is widened to int,
# which is why the reprs below show `count(1)` rather than `count(True)`
assert [x for _, x in zip(range(2), itertools.count(True))] == [1, 2]
assert [x for _, x in zip(range(3), itertools.count(0, True))] == [0, 1, 2]
assert repr(itertools.count(True)) == 'count(1)'
assert repr(itertools.count(5, True)) == 'count(5)'

# === count: promotion to big integers ===
big = itertools.count(2**62, 2**62)
assert [next(big) for _ in range(3)] == [4611686018427387904, 9223372036854775808, 13835058055282163712]
assert next(itertools.count(2**70)) == 1180591620717411303424

# === count: repr ===
# The step is shown unless it is an *integer* equal to 1.
assert repr(itertools.count()) == 'count(0)'
assert repr(itertools.count(10)) == 'count(10)'
assert repr(itertools.count(10, 2)) == 'count(10, 2)'
assert repr(itertools.count(0, 1.0)) == 'count(0, 1.0)'
assert repr(itertools.count(0, True)) == 'count(0)'
assert repr(itertools.count(2.5, 0.5)) == 'count(2.5, 0.5)'
assert repr(itertools.count(2**70)) == 'count(1180591620717411303424)'
# repr tracks the position, not the start
c5 = itertools.count(0, 2)
next(c5)
assert repr(c5) == 'count(2, 2)'

# === count: protocol ===
c6 = itertools.count()
assert iter(c6) is c6
assert bool(itertools.count())
assert str(type(itertools.count())) == "<class 'itertools.count'>"
# distinct iterators never compare equal, but one is equal to itself
assert (itertools.count() == itertools.count()) is False, 'distinct counts differ'
c7 = itertools.count()
assert (c7 == c7) is True, 'identity equality'

# === count: errors ===
# A non-number start OR step gives the same single message, checked after binding.
for bad in [lambda: itertools.count('x'), lambda: itertools.count(1, 'x'), lambda: itertools.count(step='x')]:
    try:
        bad()
        assert False, 'expected TypeError for non-numeric count argument'
    except TypeError as exc:
        assert str(exc) == 'a number is required'

try:
    itertools.count(1, 2, 3)
    assert False, 'expected TypeError for too many count arguments'
except TypeError as exc:
    assert str(exc) == 'count() takes at most 2 arguments (3 given)'

# arity is counted over positionals AND keywords together
try:
    itertools.count(1, 2, step=3)
    assert False, 'expected TypeError for count arity over the total'
except TypeError as exc:
    assert str(exc) == 'count() takes at most 2 arguments (3 given)'

try:
    itertools.count(bad=1)
    assert False, 'expected TypeError for unexpected count keyword'
except TypeError as exc:
    assert str(exc) == "count() got an unexpected keyword argument 'bad'"

# === repeat: basic ===
assert list(itertools.repeat(7, 3)) == [7, 7, 7]
assert list(itertools.repeat(7, 0)) == []
assert list(itertools.repeat(9, -1)) == []
assert list(itertools.repeat(9, times=2)) == [9, 9]
assert list(itertools.repeat(times=2, object=9)) == [9, 9]
assert list(itertools.repeat(9, True)) == [9]
assert tuple(itertools.repeat('x', 3)) == ('x', 'x', 'x')
assert sum(itertools.repeat(2, 4)) == 8
r = itertools.repeat('a', 2)
assert [next(r), next(r)] == ['a', 'a']
assert next(r, 'exhausted') == 'exhausted'
# an omitted `times` repeats forever
ri = itertools.repeat(5)
assert [next(ri) for _ in range(3)] == [5, 5, 5]

# the SAME object comes back each time, never a copy
obj = [1]
rp = itertools.repeat(obj, 2)
a = next(rp)
b = next(rp)
assert a is b
assert a is obj

# === repeat: repr ===
# The count shown is what is LEFT, so it shrinks as the iterator is consumed.
assert repr(itertools.repeat(7)) == 'repeat(7)'
assert repr(itertools.repeat(7, 3)) == 'repeat(7, 3)'
assert repr(itertools.repeat([1, 2], 2)) == 'repeat([1, 2], 2)'
r2 = itertools.repeat('a', 3)
next(r2)
assert repr(r2) == "repeat('a', 2)"
r3 = itertools.repeat(1, 2)
assert list(r3) == [1, 1]
assert repr(r3) == 'repeat(1, 0)'
assert repr(itertools.repeat(itertools.repeat(1, 1), 2)) == 'repeat(repeat(1, 1), 2)'

# === repeat: protocol ===
r4 = itertools.repeat(1, 2)
assert iter(r4) is r4
assert str(type(itertools.repeat(1))) == "<class 'itertools.repeat'>"
assert 3 in itertools.repeat(3, 2)

# === repeat: errors ===
# `times` goes through the same coercion as CPython's `n` format unit.
for bad_times in ['z', 2.0, None]:
    try:
        itertools.repeat(9, bad_times)
        assert False, 'expected TypeError for non-integer times'
    except TypeError as exc:
        assert str(exc) == f"'{type(bad_times).__name__}' object cannot be interpreted as an integer"

try:
    itertools.repeat(9, 2**70)
    assert False, 'expected OverflowError for oversized times'
except OverflowError as exc:
    assert str(exc) == 'Python int too large to convert to C ssize_t'

try:
    itertools.repeat()
    assert False, 'expected TypeError for missing repeat object'
except TypeError as exc:
    assert str(exc) == "repeat() missing required argument 'object' (pos 1)"

# a missing required argument is reported before an unexpected keyword
try:
    itertools.repeat(bad=1)
    assert False, 'expected TypeError for missing repeat object'
except TypeError as exc:
    assert str(exc) == "repeat() missing required argument 'object' (pos 1)"

try:
    itertools.repeat(1, 2, 3)
    assert False, 'expected TypeError for too many repeat arguments'
except TypeError as exc:
    assert str(exc) == 'repeat() takes at most 2 arguments (3 given)'

try:
    itertools.repeat(9, 'z', times=1)
    assert False, 'expected TypeError for repeat arity over the total'
except TypeError as exc:
    assert str(exc) == 'repeat() takes at most 2 arguments (3 given)'