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数据类型

数据类型#

import sys

数字#

a = 3
b = 4
c = 5.66
d = 8.0
e = complex(c, d)
f = complex(float(a), float(b))

print ("a is type" , type(a))
print ("b is type" , type(b))
print ("c is type" , type(c))
print ("d is type" , type(d))
print ("e is type" , type(e))
print ("f is type" , type(f))

a is type <class 'int'>
b is type <class 'int'>
c is type <class 'float'>
d is type <class 'float'>
e is type <class 'complex'>
f is type <class 'complex'>

print(a + b)
print(d / c)
print (b / a)
print (b // a)
print (e)
print (e + f)

7
1.4134275618374559
1.3333333333333333
1
(5.66+8j)
(8.66+12j)

print ("e's real part is: " , e.real)
print ("e's imaginary part is: " , e.imag)
print (sys.float_info)

e's real part is:  5.66
e's imaginary part is:  8.0
sys.float_info(max=1.7976931348623157e+308, max_exp=1024, max_10_exp=308, min=2.2250738585072014e-308, min_exp=-1021, min_10_exp=-307, dig=15, mant_dig=53, epsilon=2.220446049250313e-16, radix=2, rounds=1)

字符串#

age = 3
name = "Tom"
print("{0} was {1} years old".format(name, age))
print(name + " was " + str(age) + " years old")
print("What's your name? \nTom")

Tom was 3 years old
Tom was 3 years old
What's your name? 
Tom

字面值#

6, 2.24, 3.45e-3, "This is a string"

(6, 2.24, 0.00345, 'This is a string')

变量#

identifier = 8

列表#

number_list = [1, 3, 5, 7, 9]
string_list = ["abc", "bbc", "python"]
mixed_list = ['python', 'java', 3, 12]

second_num = number_list[1]
third_string = string_list[2]
fourth_mix = mixed_list[3]

print("second_num: {0} third_string: {1} fourth_mix: {2}".format(second_num, third_string, fourth_mix))

second_num: 3 third_string: python fourth_mix: 12

print("number_list before: " + str(number_list))
number_list[1] = 30
print("number_list after: " + str(number_list))

number_list before: [1, 3, 5, 7, 9]
number_list after: [1, 30, 5, 7, 9]

print("mixed_list before delete: " + str(mixed_list))
del mixed_list[2]
print("mixed_list after delete: " + str(mixed_list))

mixed_list before delete: ['python', 'java', 3, 12]
mixed_list after delete: ['python', 'java', 12]

print(len([1,2,3])) #长度
print([1,2,3] + [4,5,6]) #组合
print(['Hello'] * 4) #重复
print(3 in [1,2,3]) #某元素是否在列表中

3
[1, 2, 3, 4, 5, 6]
['Hello', 'Hello', 'Hello', 'Hello']
True

abcd_list =['a', 'b', 'c', 'd'] 
print(abcd_list[1])
print(abcd_list[-2])
print(abcd_list[1:])
print(abcd_list[:-1])

b
c
['b', 'c', 'd']
['a', 'b', 'c']

a_list = [1, 3, 5, 7, 9]

for i in a_list:
    print(i)

1
3
5
7
9

列表操作包含以下函数:

  1. cmp(list1, list2)：比较两个列表的元素

  2. len(list)：列表元素个数

  3. max(list)：返回列表元素最大值

  4. min(list)：返回列表元素最小值

  5. list(seq)：将元组转换为列表

列表操作包含以下方法:

  1. list.append(obj)：在列表末尾添加新的对象

  2. list.count(obj)：统计某个元素在列表中出现的次数

  3. list.extend(seq)：在列表末尾一次性追加另一个序列中的多个值（用新列表扩展原来的列表）

  4. list.index(obj)：从列表中找出某个值第一个匹配项的索引位置

  5. list.insert(index, obj)：将对象插入列表

  6. list.pop(obj=list[-1])：移除列表中的一个元素（默认最后一个元素），并且返回该元素的值

  7. list.remove(obj)：移除列表中某个值的第一个匹配项

  8. list.reverse()：反向列表中元素

  9. list.sort([func])：对原列表进行排序

元组#

a_tuple = (2,) #创建只有一个元素的tuple，需要用逗号结尾消除歧义
mixed_tuple = (1, 2, ['a', 'b'])

print(a_tuple)
print("mixed_tuple: " + str(mixed_tuple))

(2,)
mixed_tuple: (1, 2, ['a', 'b'])

mixed_tuple[2][0] = 'c'
mixed_tuple[2][1] = 'd'
print("mixed_tuple: " + str(mixed_tuple))

mixed_tuple: (1, 2, ['c', 'd'])

v = ('a', 'b', 'e')
(x, y, z) = v

print(v)
print(x, y, z)

('a', 'b', 'e')
a b e

a_tuple = (1, 3, 5, 7, 9)

for i in a_tuple:
    print(i)

1
3
5
7
9

字典#

phone_book = {'Tom': 123, "Jerry": 456, 'Kim': 789}
mixed_dict = {"Tom": 'boy', 11: 23.5}
print("Tom's number is " + str(phone_book['Tom']))
print('Tom is a ' + mixed_dict['Tom'])

Tom's number is 123
Tom is a boy

phone_book['Tom'] = 999
phone_book['Heath'] = 888
print("phone_book: " + str(phone_book))

phone_book: {'Tom': 999, 'Jerry': 456, 'Kim': 789, 'Heath': 888}

phone_book.update({'Ling':159, 'Lili':247})
print("updated phone_book: " + str(phone_book))

updated phone_book: {'Tom': 999, 'Jerry': 456, 'Kim': 789, 'Heath': 888, 'Ling': 159, 'Lili': 247}

del phone_book['Tom']
print("phone_book after deleting Tom: " + str(phone_book)) 

phone_book after deleting Tom: {'Jerry': 456, 'Kim': 789, 'Heath': 888, 'Ling': 159, 'Lili': 247}

phone_book.clear()
print("after clear: " + str(phone_book))

after clear: {}

del phone_book
# print("after del: " + str(phone_book)) # Error

list_dict = {('Name'): 'John', 'Age':13} # OK
# list_dict = {['Name']: 'John', 'Age':13} # Error

a_dict = {'Tom':'111', 'Jerry':'222', 'Cathy':'333'}

for ele in a_dict:
    print(ele)
    print(a_dict[ele])
    
for key, elem in a_dict.items():
    print(key, elem)

Tom
111
Jerry
222
Cathy
333
Tom 111
Jerry 222
Cathy 333

Python字典包含了以下内置函数：

  1. cmp(dict1, dict2)：比较两个字典元素。

  2. len(dict)：计算字典元素个数，即键的总数。

  3. str(dict)：输出字典可打印的字符串表示。

  4. type(variable)：返回输入的变量类型，如果变量是字典就返回字典类型。

Python字典包含了以下内置方法：

  1. radiansdict.clear()：删除字典内所有元素

  2. radiansdict.copy()：返回一个字典的浅复制

  3. radiansdict.fromkeys()：创建一个新字典，以序列 seq 中元素做字典的键，val 为字典所有键对应的初始值

  4. radiansdict.get(key, default=None)：返回指定键的值，如果值不在字典中返回 default 值

  5. radiansdict.has_key(key)：如果键在字典 dict 里返回 true，否则返回 false

  6. radiansdict.items()：以列表返回可遍历的(键, 值) 元组数组

  7. radiansdict.keys()：以列表返回一个字典所有的键

  8. radiansdict.setdefault(key, default=None)：和 get() 类似, 但如果键不已经存在于字典中，将会添加键并将值设为 default

  9. radiansdict.update(dict2)：把字典 dict2 的键/值对更新到 dict 里

  10. radiansdict.values()：以列表返回字典中的所有值

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