基于网络课程《Python全栈开发专题》 记录笔记，请支持正版课程。
print()命名参数
# print， sep命令参数
print('Ruby', 'Python', 'java', sep=' | ')
# print， end命令参数
print('Hello ', end='')
print('World')
赋值操作
x, y = 10, 20
print(x, y) # 10 20
# 交换两个变量的值
x, y = y, x
print(x, y) # 20 10
x += 1
print(x) # 21
Boolean类型
以下都等效于False：None, 0, "",(), [], {}
print('None =', bool(None))
print('0 =', bool(0))
print('\'\' =', bool(''))
print('() =', bool(()))
print('[] =', bool([]))
print('{} =', bool({}))
Python中，True就是1，False就是0
print('' == False) # False
print([] == False) # False
print(bool('') == False) # True
# 数字0 == False; 1 == True
print(0 == False) # True
print(1 == True) # True
print(2 == True) # False
print(bool(2) == True) # True
print(12 + True + False) # 13
条件判断语句: if/else/elif
name = input("Your name:")
if name.startswith("A"):
print("Your name start with A.")
elif name.startswith("B"):
print("Your name start with B.")
if name.endswith("B"):
print("Mr. BB")
elif name.endswith("C"):
print("Mr. BC")
else:
print("Mr. Bx")
else:
print("Your name start with others.")
if - else 单行写法
'''
当if为真，b = a，否则 ""
'''
a = [1,2,3]
b = a if len(a) != 0 else ""
b = [1,2,3]#结果
a = []
b = a if len(a) != 0 else ""
b = ""#结果
比较运算符
is / is not
# is 判断是否为同一个对象
# is not
x = 1
m = 1
z = x
y = (x+1)
print(x is z) # True
print(x is y) # False
print(x is not y) #True
in / not in
x = 5
y = 6
all = [1, 2, 5]
print(x in all) # True
print(y in all) # False
print(x not in all) # True
and / or / not
print(1 == 1 and 1 < 2 or 1 > 2)
断言
value = 20
assert(value < 5)
'''
控制台抛出异常：
Traceback (most recent call last):
File "H:\PythonWorkSpace\first-python\src\First.py", line 3, in
assert(value < 5)
AssertionError
'''
while循环
x = 0
while x <= 10:
print(x)
x += 1
for 循环
nums = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
for n in nums:
print(n, end=" ")
names = ['Tom', 'Jerry', 'Kitty']
# 等效： for i in range(0, len(names)):
for i in range(len(names)):
print(names[i], end=" ")
break & continue
略
while / for ... else
如果循环中break了，不走else。else代码块仅在循环正常退出时执行。
x = 0
while x <= 3:
if x == 2:
print()
print('do break ...')
break
print(x, end=" ")
x += 1
else:
print()
print('no break work:', x);
exec / eval
一个程序中，多次使用exec()，共享上下文：
exec('i = 1')
exec('i += 1')
exec('print(i)'); # 2
exec()和也程序共享上下文：
x = 5
exec('print(x)') # 5
exec('x += 1')
print(x) # 6
eval()执行一个表达式，有返回值。exec()没有返回值。
练习：一个简单的Python控制台
codes = ""
while True:
code = input(">>> ")
if code == "":
print('=====', codes, '=====', sep='\n')
print('输出：', end=' ')
exec(codes)
codes = ""
continue
codes += code + '\n'
if codes == "exit()" + '\n':
print('Bye Bye ...')
break
练习：输出一个菱形
Python中，数字可以和字符乘！
# 打印菱形
# 打印n个'*', 宽度为width, 居中显示
# def printer(n, width):
# s, i = "", 0;
# while i < n:
# i += 1
# s += '*'
# print(format(s, '^' + str(width)))
# 打印菱形
def buildPicture(line):
maxLine = (line - 1) / 2 # 中间最宽的行
# i 遍历行号
# x 每行要打印的“*”个数
i, x = 1, 1
while i <= line:
print(format(x * '*', '^' + str(line)))
if i <= maxLine:
x += 2
else:
x -= 2
i += 1
while True:
print('---------------------------------------');
line = int(input('请输入行数（输入0退出）:'))
if line == 0:
print('Bye Bye!')
break
elif not line % 2 :
print('请输入一个奇数！')
continue
buildPicture(line)
练习：Python版九九乘法表
num = [1, 2, 3, 4, 5, 6, 7, 8, 9]
for i in num:
for j in num:
if i < j:
continue
print(j, i, sep=" * ", end=' = ')
print(format(i*j, '>2'), end=" ")
print()
print(format('\u6211\u7231\u5E2D\u59DD\u6850', '=^110'))