python3 快速上手（总结）

    今天上班，没有什么实际的任务，闲着无聊抽空在网上搜了搜python3的内容。这篇就是copy+总结。自己动手尝试了一下

1，print

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

 

* input("某字符串")函数:显示"某字符串",并等待用户输入. 
* print()函数:如何打印.

2，字符串和数字

a = 2b = "test"c = str(a)+ bprint("c is %s" % (c))d = "1111"e = a + int(d)print("e is %i" % (e) )

用int和str函数将字符串和数字进行转换 

3，列表

#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 charactersl=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)

 列表长度是动态的,可任意添加删除元素. 

注意 []左边包括，右边不包括。eg：b=word[1:3] #word[1],word[2]没有3。

4,字典（前些天编了一个vba真是用够这个数据类型了，大学期间都没有用过几次）

x = {1:'可爱多',2:'妙脆角',3:'果粒橙'}   #这三个好像被没有什么联系print(x[1])print(x[2])print(x[3])for i in x :    print ( "key is %i and item is %s" %(i,x[i]))

这个没什么好说的 字典类型和for循环的调用

5，字符串

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 charactersl=len(word)print ("Length of word is: "+ str(l)) 

python的字符串有没有发现和元组的操作很像~

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

6，条件与循环

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

7,函数

def sum(a,b,c,d)    return a+b+c-dfunc = sumr = func(5,6,7,8)print(r)

答案是10

还有一个python好用的内置函数：range

a =range (1,10)for i in a:    print(i)

range函数：

函数原型：range（start， end， scan):

参数含义：start:计数从start开始。默认是从0开始。例如range（5）等价于range（0， 5）;

              end:技术到end结束，但不包括end.例如：range（0， 5） 是[0, 1, 2, 3, 4]没有5

              scan：每次跳跃的间距，默认为1。例如：range（0， 5） 等价于 range(0, 5, 1)

8，异常处理

#! /usr/bin/pythons=input("Input your age:")if s =="":    raise Exception("Input must no be empty.")try:    i=int(s)except Exception as err:    print(err)finally: # Clean up action    print("Goodbye!") 

9，文件处理

#! /usr/bin/pythonspath="D:/download/baa.txt"f=open(spath,"w") # Opens file for writing.Creates this file doesn't exist.f.write("First line 1.\n")f.writelines("First line 2.")f.close()f=open(spath,"r") # Opens file for readingfor line in f:  print("每一行的数据是:%s"%line)f.close() 

open的参数:r表示读,w写数据,在写之前先清空文件内容,a打开并附加内容.