Python2 编程入门

[]
[1]
[1, 2, 3, 4, 5, 6, 7, 8, 12]
[1, "two", 3, 4.0, ["a", "b"], (5,6)]

()
(1,)                  # 1个元素的tuple，逗号是必须的
(1, 2, 3, 4, 5, 6, 7, 8, 12)
(1, "two", 3L, 4.0, ["a", "b"], (5, 6))

x = [1, 2, 3, 4]
y = tuple(x)       #(1, 2, 3, 4)

x = {1: "one", 2: "two"}
x["first"] = "one"
x[("Delorme", "Ryan", 1995)] = (1, 2, 3)

>>> list(x.keys())
['first', 2, 1, ('Delorme', 'Ryan', 1995)]

>>> x[1]
'one'
>>> x.get(1, "not available")
'one'
>>> x.get(4, "not available")
'not available'

>>> x = set([1, 2, 3, 1, 3, 5])
 b
>>> x
{1, 2, 3, 5}

>>> 1 in x
True
>>> 4 in x
False
>>>

"A string in double quotes can contain 'single quote' characters."
'A string in single quotes can contain "double quote" characters.'
'''\tA string which starts with a tab; ends with a newline character.\n'''
"""This is a triple double quoted string, the only kind that can
contain real newlines."""

e = 2.718
x = [1, "two", 3, 4.0, ["a", "b"], (5, 6)]

print("The constant e is:", e, "and the list x is:", x)

# >>> The constant e is: 2.718 and the list x is: [1, 'two', 3, 4.0, ['a', 'b'], (5, 6)]

print("the value of %s is: %.2f" % ("e", e))
# >>> the value of e is: 2.72

>>> f = open("myfile", "w")
>>> f.write("First line with necessary newline character\n")
>>> f.write("Second line to write to the file\n")
>>> f.close()

>>> f = open("myfile", "r")
>>> line1 = f.readline()
>>> line2 = f.readline()
>>> f.close()

>>> print(line1, line2)
First line with necessary newline character
Second line to write to the file

>>> import os
>>> print(os.getcwd())
c:\My Documents\test
>>> os.chdir(os.path.join("c:\\", "My Documents", "images"))
>>> filename = os.path.join("c:\\", "My Documents", "test", "myfile")
>>> print(filename)
c:\My Documents\test\myfile

>>> f = open(filename, "r")
>>> print(f.readline())
First line with necessary newline character
>>> f.close()

x = 5
if x < 5:
    y = -1
    z = 5
elif x > 5:
    y = 1
    z = 11
else:
    y = 0
    z = 10
print(x, y, z)

u, v, x, y = 0, 0, 100, 30
while x > y:
    u = u + y
    x = x - y
    if x < y + 2:
        v = v + x
        x = 0
    else:
        v = v + y + 2
        x = x - y - 2
print(u, v)

item_list = [3, "string1", 23, 14.0, "string2", 49, 64, 70]
for x in item_list:
    if not isinstance(x, int):
        continue
    if not x % 7:
        print("found an integer divisible by seven: %d" % x)
        break

def funct1(x, y, z):
    value = x + 2*y + z**2
    if value > 0:
        return x + 2*y + z**2
    else:
        return 0

>>> u, v = 3, 4
>>> funct1(u, v, 2)
15
>>> funct1(u, z=v, y=2)  # 调用函数，可以使用参数名，指定值
23

def funct2(x, y=1, z=1):   # 定义参数的缺省值
    return x + 2 * y + z ** 2

>>> funct2(3, z=4)
21

def funct3(x, y=1, z=1, *tup):  # 最后一个函数参数，如果指定成带星号，剩余的实参会一股脑打包成tuple，赋给这个参
    print((x, y, z) + tup)

>>> funct3(2)
(2, 1, 1)
>>> funct3(1, 2, 3, 4, 5, 6, 7, 8, 9)
(1, 2, 3, 4, 5, 6, 7, 8, 9)

def funct4(x, y=1, z=1, **kwargs):  # 最后一个函数参数，如果指定成带2个星号，剩余的实参会一股脑打包成 dictionary
    print(x, y, z, kwargs)
>>> funct4(1, 2, m=5, n=9, z=3)
1 2 3 {'n': 9, 'm': 5}

class EmptyFileError(Exception):
    # 定义了一个错误类
    pass
filenames = ["myfile1", "nonExistent", "emptyFile", "myfile2"]
for file in filenames:
    try:
        f = open(file, 'r')
        line = f.readline()
        if line == "":
            f.close()
        raise EmptyFileError("%s: is empty" % file)
    except IOError as error:
        print("%s: could not be opened: %s" % (file, error.strerror)）
    except EmptyFileError as error:
        print(error)
    else:
        # else 代码块可选，如果try块中没发生exception，则执行
        print("%s: %s" % (file, f.readline()))
    finally:
        # 可选，不管try块中有无生exception，都执行
        print("Done processing", file)

# 使用 with 和 context manager 读取文件内容
# 这里 context manager 是预定义的，自动清除打开的file
filename = "myfile.txt"
with open(filename, "r") as f:
    for line in f:
        print(f)

filename = "myfile.txt"
try:
    f = open(filename, "r")
    for line in f:
        print(f)
except Exception as e:
    raise e
finally:
    f.close()

"""wo module. Contains function: words_occur()"""

# interface functions
def words_occur():
    """words_occur() - count the occurrences of words in a file."""
    # Prompt user for the name of the file to use.
    file_name = input("Enter the name of the file: ")
    # Open the file, read it and store its words in a list.
    f = open(file_name, 'r')
    word_list = f.read().split()
    f.close()

    # Count the number of occurrences of each word in the file.
    occurs_dict = {}
    for word in word_list:
        # increment the occurrences count for this word
        occurs_dict[word] = occurs_dict.get(word, 0) + 1
    # Print out the results.
    print("File %s has %d words (%d are unique)" \
        % (file_name, len(word_list), len(occurs_dict)))
    print(occurs_dict)

if __name__ == '__main__':
    words_occur()

import wo
wo.words_occur()

"""sh module. Contains classes Shape, Square and Circle"""
class Shape:
    """Shape class: has method move"""
    def __init__(self, x, y):
        self.x = x
        self.y = y
    def move(self, deltaX, deltaY):
        self.x = self.x + deltaX
        self.y = self.y + deltaY

class Square(Shape):
    """Square Class:inherits from Shape"""
    def __init__(self, side=1, x=0, y=0):
        Shape.__init__(self, x, y)
        self.side = side

class Circle(Shape):
    """Circle Class: inherits from Shape and has method area"""
    pi = 3.14159
    def __init__(self, r=1, x=0, y=0):
        Shape.__init__(self, x, y)
        self.radius = r
    def area(self):
        """Circle area method: returns the area of the circle."""
        return self.radius * self.radius * self.pi
    def __str__(self):
        return "Circle of radius %s at coordinates (%d, %d)" % (self.radius, self.x, self.y)

import sh
c1 = sh.Circle()
c2 = sh.Circle(5, 15, 20)

print(c1)
# >>> Circle of radius 1 at coordinates (0, 0)

print(c2)
# >>> Circle of radius 5 at coordinates (15, 20)