monty 0.0.21

A sandboxed, snapshotable Python interpreter written in Rust.
Documentation 
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# === Basic while loop ===
i = 0
result = []
while i < 3:
    result.append(i)
    i += 1
assert result == [0, 1, 2]

# === While with break ===
i = 0
result = []
while i < 10:
    if i == 3:
        break
    result.append(i)
    i += 1
assert result == [0, 1, 2]

# === While with continue ===
i = 0
result = []
while i < 5:
    i += 1
    if i % 2 == 0:
        continue
    result.append(i)
assert result == [1, 3, 5]

# === While with else (no break - else runs) ===
i = 0
flag = 0
while i < 3:
    i += 1
else:
    flag = 1
assert flag == 1

# === While with else (with break - else skipped) ===
i = 0
flag = 0
while i < 10:
    i += 1
    if i == 2:
        break
else:
    flag = 1
assert flag == 0

# === while True with break ===
i = 0
result = []
while True:
    result.append(i)
    i += 1
    if i >= 3:
        break
assert result == [0, 1, 2]

# === while False (never executes) ===
flag = 0
while False:
    flag = 1
assert flag == 0

# === while False with else (else runs immediately) ===
flag = 0
while False:
    flag = 1
else:
    flag = 2
assert flag == 2

# === Nested while loops ===
i = 0
result = []
while i < 2:
    j = 0
    while j < 2:
        result.append((i, j))
        j += 1
    i += 1
assert result == [(0, 0), (0, 1), (1, 0), (1, 1)]

# === Nested while with break inner ===
i = 0
result = []
while i < 3:
    j = 0
    while j < 3:
        if j == 1:
            break
        result.append((i, j))
        j += 1
    i += 1
assert result == [(0, 0), (1, 0), (2, 0)]

# === For inside while ===
i = 0
result = []
while i < 2:
    for j in ['a', 'b']:
        result.append((i, j))
    i += 1
assert result == [(0, 'a'), (0, 'b'), (1, 'a'), (1, 'b')]

# === While inside for ===
result = []
for i in [0, 1]:
    j = 0
    while j < 2:
        result.append((i, j))
        j += 1
assert result == [(0, 0), (0, 1), (1, 0), (1, 1)]

# === Complex condition with and ===
i = 0
j = 10
result = []
while i < 5 and j > 5:
    result.append((i, j))
    i += 1
    j -= 1
assert result == [(0, 10), (1, 9), (2, 8), (3, 7), (4, 6)]

# === Complex condition with or ===
i = 5
count = 0
while i < 3 or count < 2:
    count += 1
    i += 1
assert count == 2


# === While with function call condition ===
def check(n):
    return n < 3


i = 0
result = []
while check(i):
    result.append(i)
    i += 1
assert result == [0, 1, 2]

# === Continue does not skip else ===
i = 0
flag = 0
while i < 3:
    i += 1
    if i == 2:
        continue
else:
    flag = 1
assert flag == 1

# === Nested while - break outer via flag ===
i = 0
result = []
done = False
while i < 3 and not done:
    j = 0
    while j < 3:
        if i == 1 and j == 1:
            done = True
            break
        result.append((i, j))
        j += 1
    i += 1
assert result == [(0, 0), (0, 1), (0, 2), (1, 0)]

# === While with negative condition ===
i = 5
result = []
while not i == 3:
    result.append(i)
    i -= 1
assert result == [5, 4]

# === Nested while with inner else ===
i = 0
result = []
while i < 2:
    j = 0
    while j < 2:
        result.append(j)
        j += 1
    else:
        result.append('inner-else')
    i += 1
assert result == [0, 1, 'inner-else', 0, 1, 'inner-else']

# === Break in nested while skips inner else ===
i = 0
result = []
while i < 2:
    j = 0
    while j < 3:
        if j == 1:
            break
        result.append(j)
        j += 1
    else:
        result.append('inner-else')
    i += 1
assert result == [0, 0]


# === Exception raised by the condition is caught by an enclosing try ===
def exploding_condition():
    raise ValueError('cond boom')


log = []
try:
    while exploding_condition():
        log.append('unreached')
except ValueError as e:
    log.append(str(e))
assert log == ['cond boom']

# === Condition raising on a later evaluation, after iterations ran ===
count = 0


def cond():
    global count
    count += 1
    if count == 3:
        raise ValueError('third check')
    return True


log = []
try:
    while cond():
        log.append(count)
except ValueError as e:
    log.append(str(e))
assert log == [1, 2, 'third check']