5 字符串
比起C/C++,Python處理字符串的方式實在太讓人感動了.把字符串當列表來用吧.
#! /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))
中文和英文的字符串長度是否一樣?
#! /usr/bin/python
# -*- coding: utf8 -*-
s=input("輸入你的中文名,按回車繼續");
print ("你的名字是 : " +s)
l=len(s)
print ("你中文名字的長度是:"+str(l
'''知識點:
· 類似Java,在python3裡所有字符串都是unicode,所以長度一致.
'''
6 條件和循環語句
#! /usr/bin/python
#條件和循環語句
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))
#知識點:
# * 條件和循環語句
# * 如何得到控制檯輸入
7 函數
#! /usr/bin/python
# -*- coding: utf8 -*-
def sum(a,b):
return a+b
func = sum
r = func(5,6)
print (r)
# 提供默認值
def add(a,b=2):
return a+b
r=add(1)
print (r)
r=add(1,5)
print (r)
#一個好用的函數
#! /usr/bin/python
# -*- coding: utf8 -*-
# The range() function
a =range (1,10)
for i in a:
print (i)
a = range(-2,-11,-3) # The 3rd parameter stands for step
for i in a:
print (i)
知識點:
· Python 不用{}來控制程序結構,他強迫你用縮進來寫程序,使代碼清晰.
· 定義函數方便簡單
· 方便好用的range函數
8 異常處理
#! /usr/bin/python
s=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 文件處理
對比Java,python的文本處理再次讓人感動
#! /usr/bin/python
spath="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 reading
for line in f:
print("每一行的數據是:%s"%line)
f.close()
知識點:
· open的參數:r表示讀,w寫數據,在寫之前先清空文件內容,a打開並附加內容.
· 打開文件之後記得關閉
