# 序列协议

int `PySequence_Check`(PyObject *o)

  如果对象提供序列协议，函数返回 `1`，否则返回 `0`。 请注意它将为具有 `__getitem__()` 方法的 Python 类返回 `1`，除非它们是 `dict` 的子类，因为在一般情况下无法确定它所支持键类型。 此函数总是会成功执行。

Py_ssize_t `PySequence_Size`(PyObject *o)
Py_ssize_t `PySequence_Length`(PyObject *o)

  到哪里积分返回序列 o 中对象的数量，失败时返回 `-1`。 这相当于 Python 表达式 `len(o)`。

PyObject* `PySequence_Concat`(PyObject *o1, PyObject *o2)
  Return value: New reference.

  Return the concatenation of o1 and o2 on success, and `NULL` on failure. This is the equivalent of the Python expression `o1 + o2`.

PyObject* `PySequence_Repeat`(PyObject *o, Py_ssize_t count)
  Return value: New reference.

  Return the result of repeating sequence object o count times, or `NULL` on failure. This is the equivalent of the Python expression `o * count`.

PyObject* `PySequence_InPlaceConcat`(PyObject *o1, PyObject *o2)
  Return value: New reference.

  Return the concatenation of o1 and o2 on success, and `NULL` on failure. The operation is done in-place when o1 supports it. This is the equivalent of the Python expression `o1 += o2`.

PyObject* `PySequence_InPlaceRepeat`(PyObject *o, Py_ssize_t count)
  Return value: New reference.

  Return the result of repeating sequence object o count times, or `NULL` on failure. The operation is done in-place when o supports it. This is the equivalent of the Python expression `o *= count`.

PyObject* `PySequence_GetItem`(PyObject *o, Py_ssize_t i)
  Return value: New reference.

  Return the ith element of o, or `NULL` on failure. This is the equivalent of the Python expression `o[i]`.

PyObject* `PySequence_GetSlice`(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)
  Return value: New reference.

  Return the slice of sequence object o between i1 and i2, or `NULL` on failure. This is the equivalent of the Python expression `o[i1:i2]`.

int `PySequence_SetItem`(PyObject *o, Py_ssize_t i, PyObject *v)

  将对象 v 赋值给 o 的第 i 号元素。 失败时会引发异常并返回 `-1`；成功时返回 `0`。 这相当于 Python 语句 `o[i] = v`。 此函数 不会 改变对 v 的引用。

  If v is `NULL`, the element is deleted, however this feature is deprecated in favour of using `PySequence_DelItem()`.

int `PySequence_DelItem`(PyObject *o, Py_ssize_t i)

  删除对象 o 的第 i 号元素。 失败时返回 `-1`。 这相当于 Python 语句 `del o[i]`。

int `PySequence_SetSlice`(PyObject *o, Py_ssize_t i1, Py_ssize_t i2, PyObject *v)

  将序列对象 v 赋值给序列对象 o 的从 i1 到 i2 切片。 这相当于 Python 语句 `o[i1:i2] = v`。

int `PySequence_DelSlice`(PyObject *o, Py_ssize_t i1, Py_ssize_t i2)

  删除序列对象 o 的从 i1 到 i2 的切片。 失败时返回 `-1`。 这相当于 Python 语句 `del o[i1:i2]`。

Py_ssize_t `PySequence_Count`(PyObject *o, PyObject *value)

  返回 value 在 o 中出现的次数，即返回使得 `o[key] == value` 的键的数量。 失败时返回 `-1`。 这相当于 Python 表达式 `o.count(value)`。

int `PySequence_Contains`(PyObject *o, PyObject *value)

  确定 o 是否包含 value。 如果 o 中的某一项等于 value，则返回 `1`，否则返回 `0`。 出错时，返回 `-1`。 这相当于 Python 表达式 `value in o`。

Py_ssize_t `PySequence_Index`(PyObject *o, PyObject *value)

  返回第一个索引*i*,其中 `o[i] == value`.出错时,返回“-1”.相当于Python的``o.index(value)``表达式.

PyObject* `PySequence_List`(PyObject *o)
  Return value: New reference.

  Return a list object with the same contents as the sequence or iterable o, or `NULL` on failure. The returned list is guaranteed to be new. This is equivalent to the Python expression `list(o)`.

PyObject* `PySequence_Tuple`(PyObject *o)
  Return value: New reference.

  Return a tuple object with the same contents as the sequence or iterable o, or `NULL` on failure. If o is a tuple, a new reference will be returned, otherwise a tuple will be constructed with the appropriate contents. This is equivalent to the Python expression `tuple(o)`.

PyObject* `PySequence_Fast`(PyObject *o, const char *m)
  Return value: New reference.

  Return the sequence or iterable o as an object usable by the other `PySequence_Fast*` family of functions. If the object is not a sequence or iterable, raises `TypeError` with m as the message text. Returns `NULL` on failure.

  `PySequence_Fast*` 函数之所以这样命名，是因为它们会假定 o 是一个 `PyTupleObject` 或 `PyListObject` 并直接访问 o 的数据字段。

  作为 CPython 的实现细节，如果 o 已经是一个序列或列表，它将被直接返回。

Py_ssize_t `PySequence_Fast_GET_SIZE`(PyObject *o)

  Returns the length of o, assuming that o was returned by `PySequence_Fast()` and that o is not `NULL`. The size can also be gotten by calling `PySequence_Size()` on o, but `PySequence_Fast_GET_SIZE()` is faster because it can assume o is a list or tuple.

PyObject* `PySequence_Fast_GET_ITEM`(PyObject *o, Py_ssize_t i)
  Return value: Borrowed reference.

  Return the ith element of o, assuming that o was returned by `PySequence_Fast()`, o is not `NULL`, and that i is within bounds.

PyObject** `PySequence_Fast_ITEMS`(PyObject *o)

  Return the underlying array of PyObject pointers. Assumes that o was returned by `PySequence_Fast()` and o is not `NULL`.

  请注意,如果列表调整大小,重新分配可能会重新定位items数组.因此,仅在序列无法更改的上下文中使用基础数组指针.

PyObject* `PySequence_ITEM`(PyObject *o, Py_ssize_t i)
  Return value: New reference.

  Return the ith element of o or `NULL` on failure. Faster form of `PySequence_GetItem()` but without checking that `PySequence_Check()` on o is true and without adjustment for negative indices.