Python3 入门（一）

1、简单例子

#打开新窗口,输入:
#! /usr/bin/python
# -*- coding: utf8 -*-

s1=input("Input your name:")
print("你好,%s" % s1)

输出：

>>>

Input your name:qq

你好,qq

知识点:

* input("某字符串")函数:显示"某字符串",并等待用户输入.

* print()函数:打印.

2、字符串和数字

#! /usr/bin/python
#运行这行程序会出错,提示你字符串和数字不能连接,于是只好用内置函数进行转换
a=2
b="test"
c=str(a)+b
d="1111"
e=a+int(d)
#How to print multiply values
print ("c is %s,e is %i" % (c,e))

输出：

>>>

c is 2test,e is 1113

知识点:

* 用int和str函数将字符串和数字进行转换

* 打印以#开头,而不是习惯的//

* 打印多个参数的方式

3、列表

#! /usr/bin/python
# -*- coding: utf8 -*-
#列表类似Javascript的数组,方便易用
#定义元组
word=['a','b','c','d','e','f','g']
#如何通过索引访问元组里的元素
a=word[2]
print ("a is: "+a)
b=word[1:3]
print ("b is: ")
print (b) # index 1 and 2 elements of word.
c=word[:2]
print ("c is: ")
print (c) # index 0 and 1 elements of word.
d=word[0:]
print ("d is: ")
print (d) # All elements of word.
#元组可以合并
e=word[:2]+word[2:]
print ("e is: ")
print (e) # All elements of word.
f=word[-1]
print ("f is: ")
print (f) # The last elements of word.
g=word[-4:-2]
print ("g is: ")
print (g) # index 3 and 4 elements of word.
h=word[-2:]
print ("h is: ")
print (h) # The last two elements.
i=word[:-2]
print ("i is: ")
print (i) # Everything except the last two characters
l=len(word)
print ("Length of word is: "+ str(l))
print ("Adds new element")
word.append('h')
print (word)
#删除元素
del word[0]
print (word)
del word[1:3]
print (word)

输出：

a is: c

b is:

['b', 'c']

c is:

['a', 'b']

d is:

['a', 'b', 'c', 'd', 'e', 'f', 'g']

e is:

['a', 'b', 'c', 'd', 'e', 'f', 'g']

f is:

g

g is:

['d', 'e']

h is:

['f', 'g']

i is:

['a', 'b', 'c', 'd', 'e']

Length of word is: 7

Adds new element

['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']

['b', 'c', 'd', 'e', 'f', 'g', 'h']

['b', 'e', 'f', 'g', 'h']

>>>

知识点:

* 列表长度是动态的,可任意添加删除元素.

* 用索引可以很方便访问元素,甚至返回一个子列表

* 更多方法请参考Python的文档

4、字典

#! /usr/bin/python
x={'a':'aaa','b':'bbb','c':12}
print (x['a'])
print (x['b'])
print (x['c'])
for key in x:
print ("Key is %s and value is %s" % (key,x[key]))

输出：

aaa

bbb

12

Key is a and value is aaa

Key is b and value is bbb

Key is c and value is 12

>>>

知识点:

* 将他当Java的Map来用即可.

5、字符串

#! /usr/bin/python
word="abcdefg"
a=word[2]
print ("a is: "+a)
b=word[1:3]
print ("b is: "+b) # index 1 and 2 elements of word.
c=word[:2]
print ("c is: "+c) # index 0 and 1 elements of word.
d=word[0:]
print ("d is: "+d) # All elements of word.
e=word[:2]+word[2:]
print ("e is: "+e) # All elements of word.
f=word[-1]
print ("f is: "+f) # The last elements of word.
g=word[-4:-2]
print ("g is: "+g) # index 3 and 4 elements of word.
h=word[-2:]
print ("h is: "+h) # The last two elements.
i=word[:-2]
print ("i is: "+i) # Everything except the last two characters
l=len(word)
print ("Length of word is: "+ str(l))

输出：

a is: c

b is: bc

c is: ab

d is: abcdefg

e is: abcdefg

f is: g

g is: de

h is: fg

i is: abcde

Length of word is: 7

>>>

中文和英文的字符串长度是否一样?

#! /usr/bin/python
# -*- coding: utf8 -*-
s=input("输入你的中文名,按回车继续");
print ("你的名字是 : " +s)
l=len(s)
print ("你中文名字的长度是:"+str(l))

输出：

输入你的中文名,按回车继续张三

你的名字是 : 张三

你中文名字的长度是:2

>>>

知识点:

*类似Java,在python3里所有字符串都是unicode,所以长度一致.

6 条件和循环语句

#! /usr/bin/python
#条件和循环语句
x=int(input("Please enter an integer:"))
if x<0:
x=0
print ("Negative changed to zero")
elif x==0:
print ("Zero")
else:
print ("More")

# Loops List
a = ['cat', 'window', 'defenestrate']
for x in a:
print (x, len(x))

输出：

Please enter an integer:3

More

cat 3

window 6

defenestrate 12

>>>

知识点:

* 条件和循环语句

* 如何得到控制台输入