Python开发【第四篇】：Python基础之函数

三元运算

三元运算（三目运算），是对简单的条件语句的缩写。

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基本数据类型补充

set

set集合，是一个无序且不重复的元素集合

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练习：寻找差异

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需要删除：？

需要新建：？

需要更新：？ 注意：无需考虑内部元素是否改变，只要原来存在，新汇报也存在，就是需要更新

深浅拷贝

一、数字和字符串

对于 数字 和 字符串 而言，赋值、浅拷贝和深拷贝无意义，因为其永远指向同一个内存地址。

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def CPU报警邮件()
#发送邮件提醒
连接邮箱服务器
发送邮件
关闭连接

def 硬盘报警邮件()
#发送邮件提醒
连接邮箱服务器
发送邮件
关闭连接

def 内存报警邮件()
#发送邮件提醒
连接邮箱服务器
发送邮件
关闭连接

while True：

if cpu利用率 > 90%:
CPU报警邮件（）

if 硬盘使用空间 > 90%:
硬盘报警邮件（）

if 内存占用 > 80%:
内存报警邮件（）

无参数实现

def 发送邮件(邮件内容)

#发送邮件提醒
连接邮箱服务器
发送邮件
关闭连接

while True：

if cpu利用率 > 90%:
发送邮件("CPU报警了。")

if 硬盘使用空间 > 90%:
发送邮件("硬盘报警了。")

if 内存占用 > 80%:
发送邮件("内存报警了。")

有参数实现

函数的有三中不同的参数：

• 普通参数
• 默认参数
• 动态参数

# ######### 定义函数 #########

# name 叫做函数func的形式参数，简称：形参
def func(name):
print name

# ######### 执行函数 #########
#  'wupeiqi' 叫做函数func的实际参数，简称：实参
func('wupeiqi')

普通参数

def func(name, age = 18):

print "%s:%s" %(name,age)

# 指定参数
func('wupeiqi', 19)
# 使用默认参数
func('alex')

注：默认参数需要放在参数列表最后

默认参数

def func(*args):

print args

# 执行方式一
func(11,33,4,4454,5)

# 执行方式二
li = [11,2,2,3,3,4,54]
func(*li)

动态参数

def func(**kwargs):

print args

# 执行方式一
func(name＝'wupeiqi',age=18)

# 执行方式二
li = {'name':'wupeiqi', age:18, 'gender':'male'}
func(**li)

动态参数

def func(*args, **kwargs):

print args
print kwargs

动态参数

扩展：发送邮件实例

import smtplib
from email.mime.text import MIMEText
from email.utils import formataddr

msg = MIMEText('邮件内容', 'plain', 'utf-8')
msg['From'] = formataddr(["武沛齐",'wptawy@126.com'])
msg['To'] = formataddr(["走人",'424662508@qq.com'])
msg['Subject'] = "主题"

server = smtplib.SMTP("smtp.126.com", 25)
server.login("wptawy@126.com", "邮箱密码")
server.sendmail('wptawy@126.com', ['424662508@qq.com',], msg.as_string())
server.quit()

发送邮件实例

内置函数

class file(object)
def close(self): # real signature unknown; restored from __doc__
关闭文件
"""
close() -> None or (perhaps) an integer.  Close the file.

Sets data attribute .closed to True.  A closed file cannot be used for
further I/O operations.  close() may be called more than once without
error.  Some kinds of file objects (for example, opened by popen())
may return an exit status upon closing.
"""

def fileno(self): # real signature unknown; restored from __doc__
文件描述符
"""
fileno() -> integer "file descriptor".

This is needed for lower-level file interfaces, such os.read().
"""
return 0

def flush(self): # real signature unknown; restored from __doc__
刷新文件内部缓冲区
""" flush() -> None.  Flush the internal I/O buffer. """
pass

def isatty(self): # real signature unknown; restored from __doc__
判断文件是否是同意tty设备
""" isatty() -> true or false.  True if the file is connected to a tty device. """
return False

def next(self): # real signature unknown; restored from __doc__
获取下一行数据，不存在，则报错
""" x.next() -> the next value, or raise StopIteration """
pass

def read(self, size=None): # real signature unknown; restored from __doc__
读取指定字节数据
"""
read([size]) -> read at most size bytes, returned as a string.

If the size argument is negative or omitted, read until EOF is reached.
Notice that when in non-blocking mode, less data than what was requested
may be returned, even if no size parameter was given.
"""
pass

def readinto(self): # real signature unknown; restored from __doc__
读取到缓冲区，不要用，将被遗弃
""" readinto() -> Undocumented.  Don't use this; it may go away. """
pass

def readline(self, size=None): # real signature unknown; restored from __doc__
仅读取一行数据
"""
readline([size]) -> next line from the file, as a string.

Retain newline.  A non-negative size argument limits the maximum
number of bytes to return (an incomplete line may be returned then).
Return an empty string at EOF.
"""
pass

def readlines(self, size=None): # real signature unknown; restored from __doc__
读取所有数据，并根据换行保存值列表
"""
readlines([size]) -> list of strings, each a line from the file.

Call readline() repeatedly and return a list of the lines so read.
The optional size argument, if given, is an approximate bound on the
total number of bytes in the lines returned.
"""
return []

def seek(self, offset, whence=None): # real signature unknown; restored from __doc__
指定文件中指针位置
"""
seek(offset[, whence]) -> None.  Move to new file position.

Argument offset is a byte count.  Optional argument whence defaults to
(offset from start of file, offset should be >= 0); other values are 1
(move relative to current position, positive or negative), and 2 (move
relative to end of file, usually negative, although many platforms allow
seeking beyond the end of a file).  If the file is opened in text mode,
only offsets returned by tell() are legal.  Use of other offsets causes
undefined behavior.
Note that not all file objects are seekable.
"""
pass

def tell(self): # real signature unknown; restored from __doc__
获取当前指针位置
""" tell() -> current file position, an integer (may be a long integer). """
pass

def truncate(self, size=None): # real signature unknown; restored from __doc__
截断数据，仅保留指定之前数据
"""
truncate([size]) -> None.  Truncate the file to at most size bytes.

Size defaults to the current file position, as returned by tell().
"""
pass

def write(self, p_str): # real signature unknown; restored from __doc__
写内容
"""
write(str) -> None.  Write string str to file.

Note that due to buffering, flush() or close() may be needed before
the file on disk reflects the data written.
"""
pass

def writelines(self, sequence_of_strings): # real signature unknown; restored from __doc__
将一个字符串列表写入文件
"""
writelines(sequence_of_strings) -> None.  Write the strings to the file.

Note that newlines are not added.  The sequence can be any iterable object
producing strings. This is equivalent to calling write() for each string.
"""
pass

def xreadlines(self): # real signature unknown; restored from __doc__
可用于逐行读取文件，非全部
"""
xreadlines() -> returns self.

For backward compatibility. File objects now include the performance
optimizations previously implemented in the xreadlines module.
"""
pass

2.x

class TextIOWrapper(_TextIOBase):
"""
Character and line based layer over a BufferedIOBase object, buffer.

encoding gives the name of the encoding that the stream will be
decoded or encoded with. It defaults to locale.getpreferredencoding(False).

errors determines the strictness of encoding and decoding (see
help(codecs.Codec) or the documentation for codecs.register) and
defaults to "strict".

newline controls how line endings are handled. It can be None, '',
'\n', '\r', and '\r\n'.  It works as follows:

* On input, if newline is None, universal newlines mode is
enabled. Lines in the input can end in '\n', '\r', or '\r\n', and
these are translated into '\n' before being returned to the
caller. If it is '', universal newline mode is enabled, but line
endings are returned to the caller untranslated. If it has any of
the other legal values, input lines are only terminated by the given
string, and the line ending is returned to the caller untranslated.

* On output, if newline is None, any '\n' characters written are
translated to the system default line separator, os.linesep. If
newline is '' or '\n', no translation takes place. If newline is any
of the other legal values, any '\n' characters written are translated
to the given string.

If line_buffering is True, a call to flush is implied when a call to
write contains a newline character.
"""
def close(self, *args, **kwargs): # real signature unknown
关闭文件
pass

def fileno(self, *args, **kwargs): # real signature unknown
文件描述符
pass

def flush(self, *args, **kwargs): # real signature unknown
刷新文件内部缓冲区
pass

def isatty(self, *args, **kwargs): # real signature unknown
判断文件是否是同意tty设备
pass

def read(self, *args, **kwargs): # real signature unknown
读取指定字节数据
pass

def readable(self, *args, **kwargs): # real signature unknown
是否可读
pass

def readline(self, *args, **kwargs): # real signature unknown
仅读取一行数据
pass

def seek(self, *args, **kwargs): # real signature unknown
指定文件中指针位置
pass

def seekable(self, *args, **kwargs): # real signature unknown
指针是否可操作
pass

def tell(self, *args, **kwargs): # real signature unknown
获取指针位置
pass

def truncate(self, *args, **kwargs): # real signature unknown
截断数据，仅保留指定之前数据
pass

def writable(self, *args, **kwargs): # real signature unknown
是否可写
pass

def write(self, *args, **kwargs): # real signature unknown
写内容
pass

def __getstate__(self, *args, **kwargs): # real signature unknown
pass

def __init__(self, *args, **kwargs): # real signature unknown
pass

@staticmethod # known case of __new__
def __new__(*args, **kwargs): # real signature unknown
""" Create and return a new object.  See help(type) for accurate signature. """
pass

def __next__(self, *args, **kwargs): # real signature unknown
""" Implement next(self). """
pass

def __repr__(self, *args, **kwargs): # real signature unknown
""" Return repr(self). """
pass

buffer = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

closed = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

encoding = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

errors = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

line_buffering = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

name = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

newlines = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

_CHUNK_SIZE = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

_finalizing = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

3.x 三、管理上下文

为了避免打开文件后忘记关闭，可以通过管理上下文，即：

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如此方式，当with代码块执行完毕时，内部会自动关闭并释放文件资源。

在Python 2.7 及以后，with又支持同时对多个文件的上下文进行管理，即：

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lambda表达式

学习条件运算时，对于简单的 if else 语句，可以使用三元运算来表示，即：

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对于简单的函数，也存在一种简便的表示方式，即：lambda表达式

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递归

利用函数编写如下数列：

斐波那契数列指的是这样一个数列 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233，377，610，987，1597，2584，4181，6765，10946，17711，28657，46368...

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练习题

1、简述普通参数、指定参数、默认参数、动态参数的区别

2、写函数，计算传入字符串中【数字】、【字母】、【空格] 以及 【其他】的个数

3、写函数，判断用户传入的对象（字符串、列表、元组）长度是否大于5。

4、写函数，检查用户传入的对象（字符串、列表、元组）的每一个元素是否含有空内容。

5、写函数，检查传入列表的长度，如果大于2，那么仅保留前两个长度的内容，并将新内容返回给调用者。

6、写函数，检查获取传入列表或元组对象的所有奇数位索引对应的元素，并将其作为新列表返回给调用者。

7、写函数，检查传入字典的每一个value的长度,如果大于2，那么仅保留前两个长度的内容，并将新内容返回给调用者。

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8、写函数，利用递归获取斐波那契数列中的第 10 个数，并将该值返回给调用者。