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在学习python的过程中，记录的知识点如下：
1. 基本概念
变量：Variables, which store values for later use
数据类型：Data types, such as numbers and booleans
空格：Whitespace, which separates statements
注释：Comments, which make your code easier to read
算术运算：Arithmetic operations, including +, -,*, /, **（平方）and %（模，取余）
转义字符 ：/
# ：单行注释
一套三重引号 “”” “””：多行注释
# example
monty = True
python = 1.234
monty_python = python ** 2
# 账单的例子。 meal成本，tax是税率6.75%，tip是小费15%
meal = 44.50
tax = 0.0675
tip = 0.15
meal = meal + meal * tax
total = meal + meal * tip
print("%.2f" % total)2. 数据类型
Python主要有三种数据类型：字典、列表、元组。其分别由花括号，中括号，小括号表示。
如：
字典：dic={'a':12,'b':34}
列表：list=[1,2,3,4]
元组：tup=(1,2,3,4)
3. 字符串函数
len()：长度 str()：将非字符串转化为字符串格式
lower()：转化为小写 upper()：转化为大写
parrot = "Norwegian Blue"
print len(parrot) # 14
print parrot.lower() # norwegian blue
print parrot.upper() # NORWEGIAN BLUE
pi = 3.14
print str(pi) # 3.14 print "Spam and eggs"
print "Spam " + "and " +"eggs" # 注意 + 的使用
print "The value of pi is around " + str(3.14)
string_1 = "Camelot"
string_2 = "place"
print "Let's not go to %s. 'Tis a silly %s." % (string_1, string_2) # 注意% 和 ()
name = raw_input("What is your name?")
quest = raw_input("What is your quest?")
color = raw_input("What is your favorite color?")
print "Ah, so your name is %s, your quest is %s, " \
"and your favorite color is %s." % (name, quest, color)5. Datetime
#导入
from datetime import datetime
#获取当前时间，年月日
now = datetime.now()
current_month = now.month
current_day = now.day
current_year = now.year
print now #2014-01-14 03:23:19.092424
print current_month
print current_day
print current_year
print str(current_month)+"/"+str(current_day)+"/"+str( current_year) # mm/dd/yyyy
#获取小时，分，秒 打印格式 hh:mm:ss
now = datetime.now()
current_hour = now.hour
current_minute = now.minute
current_second = now.second
print str(current_hour)+":"+str(current_minute)+":"+str( current_second)6. 比较和控制流 Conditionals & Control Flow
# 例子
def clinic():
print "You've just entered the clinic!"
print "Do you take the door on the left or the right?"
answer = raw_input("Type left or right and hit 'Enter'.").lower()
if answer == "left" or answer == "l":
print "This is the Verbal Abuse Room, you heap of parrot droppings!"
elif answer == "right" or answer == "r":
print "Of course this is the Argument Room, I've told you that already!"
else:
print "You didn't pick left or right! Try again."
clinic()
clinic()
# 比较 >/>=/</<=/==/!=
bool_one = 20 + -10 * 2 > 10 % 3 % 2
bool_two = (10 + 17)**2 == 3**6
bool_three = 1**2**3 <= -(-(-1))
bool_four = 40 / 20 * 4 >= -4**2
bool_five = 100**0.5 != 6 + 4
# bool比较 and/or/not
#例子，注意冒号 (if, else, and elif)
def greater_less_equal_5(answer):
if answer > 5:
return 1
elif answer < 5:
return -1
else:
return 0
print greater_less_equal_5(4)
print greater_less_equal_5(5)
print greater_less_equal_5(6) 7. PygLatin
# 判断输入的字符串是否为空
print "Welcome to the English to Pig Latin translator!"
original = raw_input("Please input a string:")
if original != "":
print original
else:
print "empty" original.isalpha()：判断字符串是否全是字母
word[i:j]：取字符串i到j的字符串。
#例子，实现变换
pyg = 'ay'
original = raw_input('Enter a word:')
word = original.lower()
first = word[0]
if len(original) > 0 and original.isalpha():
#元音字母的处理，apple->appleay
if first == 'a' or first == 'e' or first == 'i' or first == 'o' or first == 'u':
new_word = original + pyg
print new_word
# 辅音字母的处理，deep->eepday
else:
new_word = word[1:len(original)] + first + pyg
print new_word
else: print 'empty'
#输出结果
Enter a word: apply
applyay
Enter a word: deep
eepday8. 函数 Functions
类型转化函数
int(x [,base ]) 将x转换为一个整数
long(x [,base ]) 将x转换为一个长整数
float(x ) 将x转换到一个浮点数
complex(real [,imag ]) 创建一个复数
str(x ) 将对象 x 转换为字符串
repr(x ) 将对象 x 转换为表达式字符串
eval(str ) 用来计算在字符串中的有效Python表达式,并返回一个对象
tuple(s ) 将序列 s 转换为一个元组
list(s ) 将序列 s 转换为一个列表
chr(x ) 将一个整数转换为一个字符
unichr(x ) 将一个整数转换为Unicode字符
ord(x ) 将一个字符转换为它的整数值
hex(x ) 将一个整数转换为一个十六进制字符串
oct(x ) 将一个整数转换为一个八进制字符串 #例子 注意 冒号：的使用
def tax(bill):
"""Adds 8% tax to a restaurant bill."""
bill *= 1.08
print "With tax: %f" % bill
return bill
def tip(bill):
"""Adds 15% tip to a restaurant bill."""
bill *= 1.15
print "With tip: %f" % bill
return bill
meal_cost = 100
meal_with_tax = tax(meal_cost)
meal_with_tip = tip(meal_with_tax)
# 例子 *的使用
def favorite_actors(*name):
"""Prints out your favorite actorS (plural!)"""
print "Your favorite actors are:" , name
favorite_actors("Michael Palin", "John Cleese", "Graham Chapman")
# 函数嵌套
def one_good_turn(n):
return n + 1
def deserves_another(n):
return one_good_turn(n) + 2
# 例子2 嵌套
def cube(n):
sum = n ** 3
return sum
def by_three(m):
if m % 3 == 0: return cube(m)
else: return False导入 import
import math
print math.sqrt(25)特定函数导入 用法：from module import function
from math import sqrt所有函数的导入 用法：from module import * import everything from the module
from math import *
import math # Imports the math module
everything = dir(math) # Sets everything to a list of things from math
print everything # Prints 'em all!函数 max() / min() / abs() / type()
the type() function returns the type of the data :
print type(42)
print type(4.2)
print type('spam')#输出结果：
<type 'int'>
<type 'float'>
<type 'unicode'>#若参数m是int或者float型，则返回其绝对值。
def distance_from_zero(m):
if type(m) == int or type(m) == float:
return abs(m)
else: return "Not an integer or float!"列表：list_name = [item_1, item_2, item_3,...]
空列表：empty_list = []
取值 list_name[index]，index从0开始编号
取列表的部分值 list_name[a:b] 从a开始，在b之前结束
list_name[:b] 从头开始，在b之前结束；list_name[a:] 从a开始，到列表尾部。
列表长度：len(list_name)
所涉及的函数
追加： list_name.append(item)
查找dog的位置：my_list.index("dog")
插入cat ： my_list.insert(4,"cat")
duck_index = animals.index("duck") # Use index() to find "duck"
animals.insert(duck_index,"cobra") # 插入
排序：square_list.sort()
For循环 variable是变量，表示列表list_name内的值
for variable in list_name:
# 例子
start_list = [5, 3, 1, 2, 4]
square_list = []
for x in start_list:
square_list.append(x ** 2)
square_list.sort()
print square_list字典d = {'key1' : 1, 'key2' : 2, 'key3' : 3}
索引 的作用—— 字符串 和 数字的对应
d = {'key1' : 1, 'key2' : 2, 'key3' : 3}
print d['key1'] #输出1
print d['key2'] #输出2
print d['key3'] #输出3dict_name[new_key] = new_value
# 例子
menu = {} # Empty dictionary
menu['Chicken Alfredo'] = 14.50 # Adding new key-value pair
print menu['Chicken Alfredo']
menu['pig'] = 20.40
menu['tomato'] = 2.00
menu['potata'] = 5.50
print "There are " + str(len(menu)) + " items on the menu."
print menu
# 输出
14.5
There are 4 items on the menu.
{'tomato': 2.0, 'Chicken Alfredo': 14.5, 'potata': 5.5, 'pig': 20.4}del dict_name[key_name]
dict_name[key] = new_value
# key - animal_name : value - location
zoo_animals = { 'Unicorn' : 'Cotton Candy House',
'Sloth' : 'Rainforest Exhibit',
'Bengal Tiger' : 'Jungle House',
'Atlantic Puffin' : 'Arctic Exhibit',
'Rockhopper Penguin' : 'Arctic Exhibit'}
# A dictionary (or list) declaration may break across multiple lines
# Removing the 'Unicorn' entry. (Unicorns are incredibly expensive.)
del zoo_animals['Unicorn']
# Your code here!
del zoo_animals['Sloth']
del zoo_animals['Bengal Tiger']
#zoo_animals['Arctic Exhibit']='Rockhopper Penguin'
zoo_animals['Rockhopper Penguin']='aa'
print zoo_animals
# 输出 {'Atlantic Puffin': 'Arctic Exhibit', 'Rockhopper Penguin': 'aa'}dict_name['list_key'].list_function()
Dict_name[‘list_key’].remove(VALUE) 将列表的值VALUE从Dict_name[‘list_key’]中移除
# 例子
inventory = {'gold' : 500,
'pouch' : ['flint', 'twine', 'gemstone'], # Assigned a new list to 'pouch' key
'backpack' : ['xylophone','dagger', 'bedroll','bread loaf']}
print inventory
# Adding a key 'burlap bag' and assigning a list to it
inventory['burlap bag'] = ['apple', 'small ruby', 'three-toed sloth']
# Sorting the list found under the key 'pouch'
inventory['pouch'].sort()
# Here the dictionary access expression takes the place of a list name
print inventory
# Your code here
inventory['pouch'] = ['seashell', 'strange berry', 'lint']
#inventory['backpack'] = ['xylophone','dagger', 'bedroll','bread loaf']
inventory['pouch'].sort()
inventory['backpack'].remove('dagger')
inventory['gold'] = 50
print inventory# 输出结果
{'backpack': ['xylophone', 'dagger', 'bedroll', 'bread loaf'], 'pouch': ['flint', 'twine', 'gemstone'], 'gold': 500}
{'backpack': ['xylophone', 'dagger', 'bedroll', 'bread loaf'], 'pouch': ['flint', 'gemstone', 'twine'], 'burlap bag': ['apple', 'small ruby', 'three-toed sloth'], 'gold': 500}
{'backpack': ['xylophone', 'bedroll', 'bread loaf'], 'pouch': ['lint', 'seashell', 'strange berry'], 'burlap bag': ['apple', 'small ruby', 'three-toed sloth'], 'gold': 50}10. A Day at the Supermarket 超市的例子
for 循环的应用
# List的例子
a = ["List of some sort”]
for x in a:
# Do something for every x
# A simple dictionary 字典的例子
d = {"foo" : "bar"}
for key in d:
print d[key] # prints "bar"
# 运用if/else的for循环
for item in numbers:
if condition:
# Do something
# 例子：统计"fizz"字符串的个数
def fizz_count(list):
sum = 0
for x in list:
if x == "fizz":
sum = sum + 1
return sum
print fizz_count(["fizz","buzz","fizz"])
#输出 2#例子：按照 “item price: x stock: x”的形式输出
prices = {"banana": 4,"apple": 2,"orange": 1.5,"pear": 3}
stock = {"banana": 6,"apple": 0,"orange": 32,"pear": 15}
for x in prices :
print x
print "price: "+str(prices[x])
print "stock: "+str(stock[x])
#输出结果
orange
price: 1.5
stock: 32
pear
price: 3
stock: 15
banana
price: 4
stock: 6
apple
price: 2
stock: 0
#例子：求卖出所有商品的总收入
prices = {"banana": 4,"apple": 2,"orange": 1.5,"pear": 3}
stock = {"banana": 6,"apple": 0,"orange": 32,"pear": 15}
for x in prices :
print x
print "price: "+str(prices[x])
print "stock: "+str(stock[x])
sum = 0
for x in prices :
sum = sum + prices[x] * stock[x]
print sum
#输出 117.0
# 超市购物的例子
# stock为库存，prices为单价，只有在有库存的情况，才能出售。每售出一商品，库存减一。
shopping_list = ["banana", "orange", "apple"]
stock = { "banana": 6, "apple": 0, "orange": 32, "pear": 15 }
prices = { "banana": 4, "apple": 2, "orange": 1.5, "pear": 3 }
#统计价格
def compute_bill(food):
total = 0
for x in food:
if stock[x] > 0:
total += prices[x]
stock[x] -=1
return total
#test
print compute_bill(["banana"])
print compute_bill(["apple","orange"])
print compute_bill(prices)
#输出
4
1.5
8.511. Student Becomes the Teacher
实例：记录学生成绩等信息
#学生名单
students = [lloyd, alice, tyler]
#学生信息
lloyd = {
"name": "Lloyd",
"homework": [90.0, 97.0, 75.0, 92.0],
"quizzes": [88.0, 40.0, 94.0],
"tests": [75.0, 90.0]
}
alice = {
"name": "Alice",
"homework": [100.0, 92.0, 98.0, 100.0],
"quizzes": [82.0, 83.0, 91.0],
"tests": [89.0, 97.0]
}
tyler = {
"name": "Tyler",
"homework": [0.0, 87.0, 75.0, 22.0],
"quizzes": [0.0, 75.0, 78.0],
"tests": [100.0, 100.0]
}
#求平均值
def average(lst):
sum = 0
n = 0
for i in lst:
sum += i
n += 1.0
return sum/n
#加权平均数
def get_average(student):
sum = 0
for key in student:
if key == "homework":
sum += average(student["homework"]) * 0.1
if key == "quizzes":
sum += average(student["quizzes"]) * 0.3
if key == "tests":
sum += average(student["tests"]) * 0.6
return sum
#成绩与等级的映射
def get_letter_grade(score):
if score >= 90 :
return "A"
if score >= 80 and score < 90 :
return "B"
if score >= 70 and score < 80 :
return "C"
if score >= 60 and score < 70 :
return "D"
if score < 60 :
return "F"
#test
print get_letter_grade(get_average(lloyd))
#班级的平均数
def get_class_average(class_list):
grade = 0
n = 0
for student in class_list:
grade += get_average(student)
n += 1
return grade/n
#test
print get_class_average(students)83.8666666667
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