算数运算

In [17]:
2 + 2
Out[17]:
4
In [18]:
50 - 5 * 6
Out[18]:
20
In [19]:
8 / 5 # 浮点数除法
Out[19]:
1.6
In [20]:
8 // 5 # 整数除法
Out[20]:
1

字符串

In [21]:
'"I\'m ZRen," he said.'
Out[21]:
'"I\'m ZRen," he said.'
In [22]:
print('"I\'m ZRen," he said.')

"I'm ZRen," he said.
In [23]:
s = 'First word.\nSecond word.'
In [24]:
s
Out[24]:
'First word.\nSecond word.'
In [25]:
print(s)

First word.
Second word.
In [26]:
'School' ' of' ' Software'# 字符串拼接，限于常量，注意空格
Out[26]:
'School of Software'
In [27]:
'b' + 2 * 'an' + 'a' # 字符串重复
Out[27]:
'banana'
In [28]:
programming = 'Programming'
In [29]:
programming[0] # 下标
Out[29]:
'P'
In [30]:
programming[-1]
Out[30]:
'g'
In [31]:
programming[5]
Out[31]:
'a'
In [32]:
programming[:2] # 切片
Out[32]:
'Pr'
In [33]:
programming[4:]
Out[33]:
'ramming'
In [34]:
programming[-2:]
Out[34]:
'ng'
In [35]:
programming[:2] + programming[2:]
Out[35]:
'Programming'

列表

In [36]:
square = [1, 4, 9, 16, 25]
In [37]:
square
Out[37]:
[1, 4, 9, 16, 25]
In [38]:
square[0]
Out[38]:
1
In [39]:
square[-1]
Out[39]:
25
In [40]:
square[-3:]
Out[40]:
[9, 16, 25]
In [41]:
square[:]
Out[41]:
[1, 4, 9, 16, 25]
In [42]:
square + square
Out[42]:
[1, 4, 9, 16, 25, 1, 4, 9, 16, 25]
In [43]:
square * 3
Out[43]:
[1, 4, 9, 16, 25, 1, 4, 9, 16, 25, 1, 4, 9, 16, 25]
In [44]:
square[2] = 0 # 列表元素可变
In [45]:
square
Out[45]:
[1, 4, 0, 16, 25]
In [46]:
square.append(-1)
In [47]:
square
Out[47]:
[1, 4, 0, 16, 25, -1]
In [48]:
len(square) # 返回列表长度
Out[48]:
6
In [49]:
a = [1, 2, 3]
b = [4, 5, 6]
c = [a, b] # 列表嵌套
In [50]:
c
Out[50]:
[[1, 2, 3], [4, 5, 6]]
In [51]:
c[0][1]
Out[51]:
2
In [52]:
x = 20
if x < 0:
    x = 0
    print("negative value of x")
elif x == 0:
    print("zero")
elif x == 1:
    print("single")
else:
    print("More")

More
In [53]:
words = ['Java', 'C++', 'Ruby']
In [54]:
for w in words:
    print(w, len(w))

Java 4
C++ 3
Ruby 4
In [55]:
for i in range(5):
    print(i)

0
1
2
3
4

函数

In [56]:
def foo():
    print("hello world")
In [57]:
def add(x, y):
    return x + y
In [58]:
print(add(3, 4))

7
In [59]:
foo()

hello world
In [60]:
import turtle
def square(length):
    turtle.forward(length)
    turtle.left(90)
    turtle.forward(length)
    turtle.left(90)
    turtle.forward(length)
    turtle.left(90)
    turtle.forward(length)
    turtle.left(90)
In [61]:
square(10)
In [62]:
def tree(len, n):
    if n <= 0:
        return
    else:
        turtle.forward(len)
        turtle.left(45)
        tree(len * 0.5, n - 1)
        turtle.right(90)
        tree(len * 0.5, n - 1)
        turtle.left(45)
        turtle.backward(len)
turtle.speed(0)
tree(200, 9)
In [63]:
def snowflake(length, threshold):
    if length < threshold:
        turtle.forward(length)
    else:
        length = length / 3
        #segment 1
        snowflake(length, threshold)
        turtle.left(60)
        #segment 2
        snowflake(length, threshold)
        turtle.right(120)
        #segment 3
        snowflake(length, threshold)
        turtle.left(60)
        #segment 4
        snowflake(length, threshold)
for i in range(3):
    snowflake(300, 10)
    turtle.right(120)
In [64]:
def triangle(length, threshold):
    if length < threshold:
        return
    else:
        for i in range(3):
            turtle.forward(length)
            triangle(length/2, threshold)
            turtle.backward(length)
            turtle.left(120)
triangle(100, 1)