从今天开始,本人就要学习Python了。
今天主要学习了Python的一些基础知识,主要涵盖了如下内容:
1、数字和表达式
在Python交互式解析器中,可以直接进行运算。
一般的数学函数可以引入math块,一些复杂的数学函数需要引入cmath块。Python支持长×××数据:1000000000L。取整运算的两种方法:(1):math.floor(X) (2) int(X)
在Python中,八进制和十六进制的书写如下:
0xAF , 010...
首数字都是零。
2、变量
Python中的变量可以包括字母、数字和下划线,但是不能以数字开头。在使用变量以前要对变量进行赋值,没有赋值的变量时没有意义的。
3、获取用户输入
两种方法:input 和 raw_input,二者的区别在于,input会假象获取的输入是合法的Python表达式,raw_input 获取的是用户的原始输入,并将其存储在字符串中。除非特殊需要,一般使用raw_input来获取用户输入。
4、字符串
通常在输入一些单双引号都有的句子或者说一些在Python中被认作具有特殊含义的字符,需要将这些特殊字符使用转义字符来加以区别。一个更好的解决类似问题的办法是使用原始字符串输入,例如:
print r' string '避免了大量使用转义字符的麻烦,但是需要指出的是,使用原始字符串输入在语句的末尾不能使用" \ ",如果必须要使用,还是要加上转义字符 " \\ "。
长字符串。如果需要输入一个很长的字符串并且需要跨越多行,那么可以使用3个单引号来代替普通引号。
unicode字符,就是在输入的字符串前加 u 。如 print u' hello world !'
数值被转换成字符串的两种机制:函数str和repr。二者的区别在于,str将数值转换成用户可以理解形式的字符串,而repr会将创建一个字符串,这个字符串是python合法形式的表达式。
5、模块
在我们使用一些非python默认函数的时候,可以使用引用模块的形式来调用函数。
可以使用以下两种方式:
(1)from 一个模块 import 函数
然后可以直接使用函数。
(2)import 一个模块
module.函数
建议使用第二种形式调用函数,因为在有些地方会导致命名的冲突。
今天练习使用的代码:
Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)] on win32 Type "copyright", "credits" or "license()" for more information. >>> 2 ** 3 8 >>> -3 **2 -9 >>> (-3) ** 2 9 >>> 1111111111111111111111111111111111111111111111111111111111111 1111111111111111111111111111111111111111111111111111111111111L >>> 11111111111111111111111111111111111111l 11111111111111111111111111111111111111L >>> 2324324523423432432432432L * 2132132143432423423432L 4955767028159349056163576467822347272465546624L >>> 0X86 134 >>> 01010101010101010101 18300341342965825L >>> x = 5 >>> x % 4 1 >>> x *9 45 >>> x+1 6 >>> y= x+1 >>> y 6 >>> print x+y 11 >>> z =x +y >>> z 11 >>> input("the meaning of life: ") the meaning of life: 34 34 >>> x = input("x: ") x: 9 >>> y =input("y: ") y: -9 >>> print x+y 0 >>> if 1 == 2:print 'One equals two ' >>> if 1 == 2: print 'One equals two ' >>> >>> if 1 ==1 : print 'One equals one ' One equals one >>> if time % 60 == 0: print 'On the hour ' Traceback (most recent call last): File "<pyshell#29>", line 1, in <module> if time % 60 == 0: print 'On the hour ' NameError: name 'time' is not defined >>> pow(2.9) Traceback (most recent call last): File "<pyshell#30>", line 1, in <module> pow(2.9) TypeError: pow expected at least 2 arguments, got 1 >>> pow(2 9) SyntaxError: invalid syntax >>> pow(2,9) 512 >>> pow(2, 2+1) 8 >>> x= input(" 你想要的数字:“) SyntaxError: EOL while scanning string literal >>> x= input(" 你想要的数字:") SyntaxError: invalid syntax >>> x = input(" 你想要的数字: ") SyntaxError: invalid syntax >>> x= input(" 123:") SyntaxError: invalid syntax >>> x = input(" 你想要的数字: ") 你想要的数字: pow (2,10) >>> x 1024 >>> abs(-1) 1 >>> 1/2 0 >>> round(1.0/2.0) 1.0 >>> floor (1,2) Traceback (most recent call last): File "<pyshell#43>", line 1, in <module> floor (1,2) NameError: name 'floor' is not defined >>> import math >>> math.floor(30.1) 30.0 >>> floor(30.9) Traceback (most recent call last): File "<pyshell#46>", line 1, in <module> floor(30.9) NameError: name 'floor' is not defined >>> math.floor(23.9) 23.0 >>> int(math.floor(20.5)) 20 >>> from math import floor >>> floor(34.1) 34.0 >>> big=math.floor >>> big(23.1) 23.0 >>> int(34.2 ) 34 >>> from math import sprt Traceback (most recent call last): File "<pyshell#56>", line 1, in <module> from math import sprt ImportError: cannot import name sprt >>> from math import sprt Traceback (most recent call last): File "<pyshell#57>", line 1, in <module> from math import sprt ImportError: cannot import name sprt >>> import math >>> math.sprt(2) Traceback (most recent call last): File "<pyshell#59>", line 1, in <module> math.sprt(2) AttributeError: 'module' object has no attribute 'sprt' >>> from math import sqrt >>> sqrt(-2) Traceback (most recent call last): File "<pyshell#61>", line 1, in <module> sqrt(-2) ValueError: math domain error >>> from math import sqrt >>> sqrt(4) 2.0 >>> imprt math SyntaxError: invalid syntax >>> import math >>> cmath.sqrt(-2) Traceback (most recent call last): File "<pyshell#66>", line 1, in <module> cmath.sqrt(-2) NameError: name 'cmath' is not defined >>> import cmath >>> cmath.sqrt(-2) 1.4142135623730951j >>> from math import sqrt >>> from cmath import sqrt >>> sqrt(3) (1.7320508075688772+0j) >>> from math import sqrt >>> sqrt(3) 1.7320508075688772 >>> ================================ RESTART ================================ >>> Hello, world >>> ================================ RESTART ================================ >>> What is your name? bing Hello, bing ! >>> x= "hello" >>> y= "world" >>> xy Traceback (most recent call last): File "<pyshell#76>", line 1, in <module> xy NameError: name 'xy' is not defined >>> x y SyntaxError: invalid syntax >>> x 'hello' >>> she's mothen SyntaxError: EOL while scanning string literal >>> >>> she\'s mother SyntaxError: unexpected character after line continuation character >>> "hello, world " 'hello, world ' >>> she Traceback (most recent call last): File "<pyshell#83>", line 1, in <module> she NameError: name 'she' is not defined >>> 'she 's mother ' SyntaxError: invalid syntax >>> ' she\ 's mother ' SyntaxError: invalid syntax >>> ' she \'s mother ' " she 's mother " >>> print ' hello world ' hello world >>> 10000000l 10000000L >>> print ' 10000L ' 10000L >>> print " 10000L " 10000L >>> 10000L 10000L >>> print 10000l 10000 >>> print repr("hello, world !") 'hello, world !' >>> print repr(10000L) 10000L >>> print str("hello, world !" ) hello, world ! >>> temp =42 >>> print "the temperature is" + temp Traceback (most recent call last): File "<pyshell#99>", line 1, in <module> print "the temperature is" + temp TypeError: cannot concatenate 'str' and 'int' objects >>> print "the temperature is" + `temp` the temperature is42 >>> print "the temperature is " + `temp` the temperature is 42 >>> name = input("what is your name ? ") what is your name ? bing Traceback (most recent call last): File "<pyshell#102>", line 1, in <module> name = input("what is your name ? ") File "<string>", line 1, in <module> NameError: name 'bing' is not defined >>> name = input("what is your name ? ") what is your name ? 1223 >>> name = input("what is your name ? "); what is your name ? 122 >>> print "hello " + name "!" SyntaxError: invalid syntax >>> print "hello " + name " ! " SyntaxError: invalid syntax >>> print "hello " + name + "!" Traceback (most recent call last): File "<pyshell#107>", line 1, in <module> print "hello " + name + "!" TypeError: cannot concatenate 'str' and 'int' objects >>> name = input("what is your name ? "); what is your name ? 123 >>> print "hello " + name + "!" Traceback (most recent call last): File "<pyshell#109>", line 1, in <module> print "hello " + name + "!" TypeError: cannot concatenate 'str' and 'int' objects >>> ================================ RESTART ================================ >>> what is your name ? 123print "hello " + name + "!" Traceback (most recent call last): File "D:/python/test", line 1, in <module> name = input("what is your name ? ") File "<string>", line 1 123print "hello " + name + "!" ^ SyntaxError: invalid syntax >>> ================================ RESTART ================================ >>> what is your name ? 123 Traceback (most recent call last): File "D:/python/test", line 2, in <module> print "hello " + name + "!" TypeError: cannot concatenate 'str' and 'int' objects >>> ================================ RESTART ================================ >>> what is your name ? "bing" hello bing! >>> print ''' This is a vert idd fdfd " hello world " there ''' This is a vert idd fdfd " hello world " there >>> print " hello, \ world ! " hello, world ! >>> print 'C:\\ on" SyntaxError: EOL while scanning string literal >>> print "C:\\ on" C:\ on >>> print ' hello, \n world ! ' hello, world ! >>> print 'c:\nowhere' c: owhere >>> print r'c:\nere\ndf' c:\nere\ndf >>> print r"this is not corrert\" SyntaxError: EOL while scanning string literal >>> print r"this is not corrert" "\\" this is not corrert\ >>> print r"this is not corrert" "\" SyntaxError: EOL while scanning string literal >>> u'hello world !' u'hello world !' >>> print u'你好' Äãoà >>> print r'你好' 你好 >>>