python help() 帮助文档 哪里不会查哪里

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help

在python中遇到不会的方法怎么办，用help查一下用法。
用法help()放入函数名，不需要加括号。首先来个套娃，查询一下help函数的用法。

help(help)

class _Helper(builtins.object)
| Define the builtin ‘help’.
|
| This is a wrapper around pydoc.help that provides a helpful message
| when ‘help’ is typed at the Python interactive prompt.
|
| Calling help() at the Python prompt starts an interactive help session.
| Calling help(thing) prints help for the python object ‘thing’.

print

然后查询一下print()方法的用法。

help(print)

print(…)
print(value, …, sep=’ ‘, end=’\n’, file=sys.stdout, flush=False)
Prints the values to a stream, or to sys.stdout by default.
Optional keyword arguments:
file: a file-like object (stream); defaults to the current sys.stdout.
sep: string inserted between values, default a space.
end: string appended after the last value, default a newline.
flush: whether to forcibly flush the stream.

a = 1
b = [2,3,4]
c = "miao"
print(a, b, c)
print(a, b, c, sep=", ")
print(a, b, c, sep="\n")
print(a, end="--")
print(b, end="--")
print(c, end="--")

1 [2, 3, 4] miao
1, [2, 3, 4], miao
1
[2, 3, 4]
miao
1–[2, 3, 4]–miao–

sys

help('sys')

或者

import sys
help(sys)

也可以

import sys
help(sys.path)

查询某个具体方法

help(sys.path.append)

append(object, /) method of builtins.list instance
Append object to the end of the list.

基础数据类型

int型数据

number = 666
help(number)

bit_length(self, /)
| Number of bits necessary to represent self in binary.
|
| >>> bin(37)
| ‘0b100101’
| >>> (37).bit_length()
| 6

number = 666
print(bin(number))
print(number.bit_length())

0b1010011010
10
数组类型

array = [1,2,3]
help(array)   

数组的一些常用方法如下

append(self, object, /)
| Append object to the end of the list.
|
| clear(self, /)
| Remove all items from list.
|
| copy(self, /)
| Return a shallow copy of the list.
|
| count(self, value, /)
| Return number of occurrences of value.
|
| extend(self, iterable, /)
| Extend list by appending elements from the iterable.
|
| index(self, value, start=0, stop=9223372036854775807, /)
| Return first index of value.
|
| Raises ValueError if the value is not present.
|
| insert(self, index, object, /)
| Insert object before index.
|
| pop(self, index=-1, /)
| Remove and return item at index (default last).
|
| Raises IndexError if list is empty or index is out of range.
|
| remove(self, value, /)
| Remove first occurrence of value.
|
| Raises ValueError if the value is not present.
|
| reverse(self, /)
| Reverse IN PLACE.
|
| sort(self, /, *, key=None, reverse=False)
| Sort the list in ascending order and return None.

help(array.append)

append(object, /) method of builtins.list instance
Append object to the end of the list.

string类型数据

string="miao"
print(type(string))
help(string)

<class ‘str’>
No Python documentation found for ‘miao’.
Use help() to get the interactive help utility.
Use help(str) for help on the str class.

help(str)

str的常用方法如下

startswith(…)
| S.startswith(prefix[, start[, end]]) -> bool
|
| Return True if S starts with the specified prefix, False otherwise.
| With optional start, test S beginning at that position.
| With optional end, stop comparing S at that position.
| prefix can also be a tuple of strings to try.
|

time

import time
help(time.time)

time(…)
time() -> floating point number
Return the current time in seconds since the Epoch.
Fractions of a second may be present if the system clock provides them.

format

help(format)

format(value, format_spec=’’, /)
Return value.format(format_spec)

format_spec defaults to the empty string.
See the Format Specification Mini-Language section of help('FORMATTING') for
details.

关于format详情可以参见print(help(‘FORMATTING’))。

help('FORMATTING')

Format String Syntax

The “str.format()” method and the “Formatter” class share the same
syntax for format strings (although in the case of “Formatter”,
subclasses can define their own format string syntax). The syntax is
related to that of formatted string literals, but there are
differences.
Format strings contain “replacement fields” surrounded by curly braces
“{}”. Anything that is not contained in braces is considered literal
text, which is copied unchanged to the output. If you need to include
a brace character in the literal text, it can be escaped by doubling:
“{{” and “}}”.

可以直接拉到例子部分。

Format examples
===============
This section contains examples of the “str.format()” syntax and
comparison with the old “%”-formatting.
In most of the cases the syntax is similar to the old “%”-formatting,
with the addition of the “{}” and with “:” used instead of “%”. For
example, “’%03.2f’” can be translated to “’{:03.2f}’”.
The new format syntax also supports new and different options, shown
in the following examples.

```python
print('{:.2f}'.format(3453.2398473))

3453.24

torch.ones

help(torch.ones)

ones(…)
ones(*size, *, out=None, dtype=None, layout=torch.strided, device=None, requires_grad=False) -> Tensor
Returns a tensor filled with the scalar value 1, with the shape defined
by the variable argument :attr:size.
Args:
size (int…): a sequence of integers defining the shape of the output tensor.
Can be a variable number of arguments or a collection like a list or tuple.
Keyword arguments:
out (Tensor, optional): the output tensor.
dtype (:class:torch.dtype, optional): the desired data type of returned tensor.
Default: if None, uses a global default (see :func:torch.set_default_tensor_type).
layout (:class:torch.layout, optional): the desired layout of returned Tensor.
Default: torch.strided.
device (:class:torch.device, optional): the desired device of returned tensor.
Default: if None, uses the current device for the default tensor type
(see :func:torch.set_default_tensor_type). :attr:device will be the CPU
for CPU tensor types and the current CUDA device for CUDA tensor types.
requires_grad (bool, optional): If autograd should record operations on the
returned tensor. Default: False.
Example::

torch.ones(2, 3)
tensor([[ 1., 1., 1.],
[ 1., 1., 1.]])

torch.ones(5)
tensor([ 1., 1., 1., 1., 1.])

np.rand.normal

features
print(help(features))

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