INT104-T1-Python

#INT104 #Python

这节课，正式开始了我们本学期的Python学习之旅。Python是一种易于学习的“解释性语言”：不需要预先编译，可以快速开发和测试代码 —— 这也是为什么 Python 文件运行的速度要比 C 为代表的编译型语言快得多的主要原因。

本篇文章总结了 tutorial 1 主要的语法知识点。（因为在这之前相信都有上学期的Java基础，所以以Python的语法特点为重点，对关键字的定义和用途不作过多解释。）
（前排提示老师给的notebook上面有这些知识的汇总，看那个也行）

Variable (变量)

x = 3
y = 4
z = x * y
answer = True
print(answer)

Types (类型)

Casting types (强制转换)

x = 10     # This is an integer
y = "20"   # This is a string
z= x + int(y)

Strings (字符串)

x = "This can be"
y = "repeated "
z = x + " " + y * 3
x = x.upper() #字符串内容大写
x = x.lower() #字符串内容小写

Multiline strings (多行字符串)

x = """ To include
multiple lines
you have to do this"""
y = " or you can\ninclude the special\n character`\\n`between lines"

Lists (列表)

# a list of strings
fruits = ["apple", "orange", "tomato", "banana"] 
fruits[2]    # indexing a list
len(fruits)  # the length of a list

# a list with integers
# Syntax : range(start point, end point, step size)
nums = list(range(0, 30, 5))
print(nums) # -> [0, 5, 10, 15, 20, 25] The end point is not included

# Slicing lists
# Syntax: List[start point : end point : step size ]
nums2 = list(range(0, 100, 5))
print(nums)
print(nums2[1:5:2])  # get from item 1(starting point) through item 5(end point, not included) with step size 2
print(nums2[0:3])    # get items 0 through 3
print(nums2[4:])     # get items 4 onwards
print(nums2[-1])     # get the last item
print(nums2[::-1])   # get the whole list backwards

# helpful functions
print(len(nums))
print(max(nums))
print(min(nums))

# lists can be of different types
mixed = [3, "Two", True, None]

Tuples(元组)

fruits = ("apple", "orange", "tomato", "banana")

那么问题来了，tuples和lists的区别是什么？
这里有一些解答：

Sets (集合)

x = {3, 3, 2, 1}       # a set created directly
y = set([1, 2, 3, 3])  # a set created from a list
x == y                 # True, x and y are the same object

Dictionaries (字典)

# Syntax: name = {key: value}
days = {"Monday": "1",
       "Tuesday": "2"}
days["Monday"]  # 1

days.update({"Saturday": "6"})

days.pop("Monday") # remove a day

print(days.keys())    # dict_keys(['Tuesday', 'Saturday'])
print(days.values())  # dict_values(['2', '6'])

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