Python教程：易学高效的编程语言

需积分: 0 123 浏览量更新于2024-07-27 收藏 295KB PDF 举报

本资源是一份由Guido van Rossum等编写的英文版Python教程，名为"Python Tutorial"，适用于Python 2.3.3版本。该教程由Fred L. Drake, Jr.编辑，并在2003年12月19日发布。Python Labs是发行方，联系邮箱为docs@python.org。版权方面，Python Software Foundation、BeOpen.com、Corporation for National Research Initiatives和Stichting Mathematisch Centrum分别对其不同部分享有版权，所有权利受到保护。 Python作为一门易学且强大的编程语言，其特点体现在高效的数据结构和简洁而有效的面向对象编程方法上。Python的优雅语法以及动态类型系统结合其解释执行特性，使其成为脚本编写和快速应用开发的理想选择，尤其在大多数平台上表现优异。该教程的核心内容包括Python解释器的介绍和广泛的标准库，这些都可在Python官方网站<http://www.python.org/>上免费获取，无论是源代码还是二进制形式，都支持主要平台的安装和分发。此外，网站还提供各种发行版和指向其他相关资源的链接，以满足用户的不同需求。学习者可以通过这份教程深入了解Python的基础知识，如变量和数据类型、控制流、函数、类和对象、模块与包等核心概念。同时，它还会指导读者如何利用标准库进行文件操作、网络编程、GUI编程以及数据处理等实际应用。通过阅读这份教程，初学者可以快速掌握Python编程基础，而有经验的开发者则能从中发现优化现有项目或探索新功能的方法。这份Python教程是Python语言学习者的宝贵资源，无论你是新手还是希望深入理解Python特性的专业人士，都能从中受益匪浅。

>>> ’spam eggs’

’spam eggs’

>>> ’doesn\’t’

"doesn’t"

>>> "doesn’t"

"doesn’t"

>>> ’"Yes," he said.’

’"Yes," he said.’

>>> "\"Yes,\" he said."

’"Yes," he said.’

>>> ’"Isn\’t," she said.’

’"Isn\’t," she said.’

String literals can span multiple lines in several ways. Continuation lines can be used, with a backslash as the last

character on the line indicating that the next line is a logical continuation of the line:

hello = "This is a rather long string containing\n\

several lines of text just as you would do in C.\n\

Note that whitespace at the beginning of the line is\

significant."

print hello

Note that newlines would still need to be embedded in the string using \n; the newline following the trailing

backslash is discarded. This example would print the following:

This is a rather long string containing

several lines of text just as you would do in C.

Note that whitespace at the beginning of the line is significant.

If we make the string literal a “raw” string, however, the \n sequences are not converted to newlines, but the

backslash at the end of the line, and the newline character in the source, are both included in the string as data.

Thus, the example:

hello = r"This is a rather long string containing\n\

several lines of text much as you would do in C."

print hello

would print:

This is a rather long string containing\n\

several lines of text much as you would do in C.

Or, strings can be surrounded in a pair of matching triple-quotes: """ or ’’’. End of lines do not need to be

escaped when using triple-quotes, but they will be included in the string.

print """

Usage: thingy [OPTIONS]

-h Display this usage message

-H hostname Hostname to connect to

"""

produces the following output:

10 Chapter 3. An Informal Introduction to Python

>>> word[-100:]

’HelpA’

>>> word[-10] # error

Traceback (most recent call last):

File "<stdin>", line 1, in ?

IndexError: string index out of range

The best way to remember how slices work is to think of the indices as pointing between characters, with the left

edge of the ﬁrst character numbered 0. Then the right edge of the last character of a string of n characters has

index n, for example:

+---+---+---+---+---+

| H | e | l | p | A |

+---+---+---+---+---+

0 1 2 3 4 5

-5 -4 -3 -2 -1

The ﬁrst row of numbers gives the position of the indices 0...5 in the string; the second row gives the corresponding

negative indices. The slice from i to j consists of all characters between the edges labeled i and j, respectively.

For non-negative indices, the length of a slice is the difference of the indices, if both are within bounds. For

example, the length of word[1:3] is 2.

The built-in function len() returns the length of a string:

>>> s = ’supercalifragilisticexpialidocious’

>>> len(s)

See Also:

Sequence Types

(../lib/typesseq.html)

Strings, and the Unicode strings described in the next section, are examples of sequence types, and support

the common operations supported by such types.

String Methods

(../lib/string-methods.html)

Both strings and Unicode strings support a large number of methods for basic transformations and searching.

String Formatting Operations

(../lib/typesseq-strings.html)

The formatting operations invoked when strings and Unicode strings are the left operand of the % operator

are described in more detail here.

3.1.3 Unicode Strings

Starting with Python 2.0 a new data type for storing text data is available to the programmer: the Unicode object.

It can be used to store and manipulate Unicode data (see http://www.unicode.org/) and integrates well with the

existing string objects providing auto-conversions where necessary.

Unicode has the advantage of providing one ordinal for every character in every script used in modern and ancient

texts. Previously, there were only 256 possible ordinals for script characters and texts were typically bound to

a code page which mapped the ordinals to script characters. This lead to very much confusion especially with

respect to internationalization (usually written as ‘i18n’ — ‘i’ + 18 characters + ‘n’) of software. Unicode

solves these problems by deﬁning one code page for all scripts.

Creating Unicode strings in Python is just as simple as creating normal strings:

3.1. Using Python as a Calculator 13

>>> u’Hello World !’

u’Hello World !’

The small ‘u’ in front of the quote indicates that an Unicode string is supposed to be created. If you want

to include special characters in the string, you can do so by using the Python Unicode-Escape encoding. The

following example shows how:

>>> u’Hello\u0020World !’

u’Hello World !’

The escape sequence \u0020 indicates to insert the Unicode character with the ordinal value 0x0020 (the space

character) at the given position.

Other characters are interpreted by using their respective ordinal values directly as Unicode ordinals. If you have

literal strings in the standard Latin-1 encoding that is used in many Western countries, you will ﬁnd it convenient

that the lower 256 characters of Unicode are the same as the 256 characters of Latin-1.

For experts, there is also a raw mode just like the one for normal strings. You have to preﬁx the opening quote

with ’ur’ to have Python use the Raw-Unicode-Escape encoding. It will only apply the above \uXXXX conversion

if there is an uneven number of backslashes in front of the small ’u’.

>>> ur’Hello\u0020World !’

u’Hello World !’

>>> ur’Hello\\u0020World !’

u’Hello\\\\u0020World !’

The raw mode is most useful when you have to enter lots of backslashes, as can be necessary in regular expressions.

Apart from these standard encodings, Python provides a whole set of other ways of creating Unicode strings on

the basis of a known encoding.

The built-in function unicode() provides access to all registered Unicode codecs (COders and DECoders).

Some of the more well known encodings which these codecs can convert are Latin-1, ASCII, UTF-8, and UTF-16.

The latter two are variable-length encodings that store each Unicode character in one or more bytes. The default

encoding is normally set to ASCII, which passes through characters in the range 0 to 127 and rejects any other

characters with an error. When a Unicode string is printed, written to a ﬁle, or converted with str(), conversion

takes place using this default encoding.

>>> u"abc"

u’abc’

>>> str(u"abc")

’abc’

>>> u"äöü"

u’\xe4\xf6\xfc’

>>> str(u"äöü")

Traceback (most recent call last):

File "<stdin>", line 1, in ?

UnicodeEncodeError: ’ascii’ codec can’t encode characters in position 0-2: ordinal not in range(128)

To convert a Unicode string into an 8-bit string using a speciﬁc encoding, Unicode objects provide an encode()

method that takes one argument, the name of the encoding. Lowercase names for encodings are preferred.

>>> u"äöü".encode(’utf-8’)

’\xc3\xa4\xc3\xb6\xc3\xbc’

14 Chapter 3. An Informal Introduction to Python

剩余99页未读，继续阅读

mas09

粉丝: 0
资源: 2

Python教程：易学高效的编程语言

Python Tutorial中英双语对照文档.md

《Python Tutorial Python》PDF

Python Tutorial Python 入门指南

Python tutorial

Python Tutorial

PythonTutorial

Python Tutorial Python

Python入门 PythonTutorial

Python Tutorial Python入门指南

PythonTutorial:Python教程

最新资源