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| author | Georg Brandl <georg@python.org> | 2008-09-13 17:18:21 (GMT) |
|---|---|---|
| committer | Georg Brandl <georg@python.org> | 2008-09-13 17:18:21 (GMT) |
| commit | 5d955ed13e4489b229fd31135aaa9280835665be (patch) | |
| tree | dbf87d436d01e9a251f011fb5282fd7b95213691 /Doc/tutorial/introduction.rst | |
| parent | d7b032841aba549f2ec532adcd83829d0126bf40 (diff) | |
| download | cpython-5d955ed13e4489b229fd31135aaa9280835665be.zip cpython-5d955ed13e4489b229fd31135aaa9280835665be.tar.gz cpython-5d955ed13e4489b229fd31135aaa9280835665be.tar.bz2 | |
Forward-port of r66447.
Diffstat (limited to 'Doc/tutorial/introduction.rst')
| -rw-r--r-- | Doc/tutorial/introduction.rst | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/Doc/tutorial/introduction.rst b/Doc/tutorial/introduction.rst index bc81d7a..57254db 100644 --- a/Doc/tutorial/introduction.rst +++ b/Doc/tutorial/introduction.rst @@ -13,9 +13,11 @@ end a multi-line command. Many of the examples in this manual, even those entered at the interactive prompt, include comments. Comments in Python start with the hash character, -``#``, and extend to the end of the physical line. A comment may appear at -the start of a line or following whitespace or code, but not within a string +``#``, and extend to the end of the physical line. A comment may appear at the +start of a line or following whitespace or code, but not within a string literal. A hash character within a string literal is just a hash character. +Since comments are to clarify code and are not interpreted by Python, they may +be omitted when typing in examples. Some examples:: @@ -96,6 +98,15 @@ A value can be assigned to several variables simultaneously:: >>> z 0 +Variables must be "defined" (assigned a value) before they can be used, or an +error will occur:: + + >>> # try to access an undefined variable + ... n + Traceback (most recent call last): + File "<stdin>", line 1, in <module> + NameError: name 'n' is not defined + There is full support for floating point; operators with mixed type operands convert the integer operand to floating point:: @@ -290,7 +301,7 @@ omitted second index defaults to the size of the string being sliced. :: >>> word[2:] # Everything except the first two characters 'lpA' -Unlike a C string, Python strings cannot be changed. Assigning to an indexed +Unlike a C string, Python strings cannot be changed. Assigning to an indexed position in the string results in an error:: >>> word[0] = 'x' @@ -409,8 +420,8 @@ About Unicode .. sectionauthor:: Marc-Andre Lemburg <mal@lemburg.com> -Starting with Python 3.0 all strings support Unicode. -(See http://www.unicode.org/) +Starting with Python 3.0 all strings support Unicode (see +http://www.unicode.org/). 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 |