Python编程基础知识点

1. 修改字符串的大小写

name = "ada loveLace"
print(name.title())   # 首字母大写，其余字母小写
print(name.lower())   # 字母全都小写
print(name.upper())   # 字母全都大写

结果为：

Ada Lovelace
ada lovelace
ADA LOVELACE

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2. 合并字符串用“+”即可

first_word = "Hello! "
second_word = "Dancy."
print(first_word + second_word)

结果为：Hello! Dancy.

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3. 使用“\t”来增加空白格

print("\tpython")

结果为：

	python

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4. 删除空白格

language = ' python '    # 左右两边都有空白
print(language.strip())   # 删除所有空格
print(language.rstrip())  # 删除右边的空格
print(language.lstrip())  # 删除左边的空格

结果为：

python
 python
python 

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5. 列表中插入、删除元素

a. insert插入元素

color = ["red", "yellow", "blue"]
color.insert(0, "green")  # 第一个参数为下标，第二个参数为需要插入的值
print(color)

结果为：['green', 'red', 'yellow', 'blue']

b. del删除任意位置的元素

color = ["red", "yellow", "blue"]
del(color[1]) 
print(color)

结果为：['red', 'blue']

b. pop删除元素

color = ["red", "yellow", "blue"]
print(color.pop())

结果为：blue

删除任意位置的元素：

color = ["red", "yellow", "blue"]
print(color.pop(1))

结果为：yellow

c. remove根据值删除元素

color = ["red", "yellow", "red", "blue"]
color.remove("red")
print(color)

结果为：['yellow', 'red', 'blue']

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6. 列表排序

a. 使用sort进行永久排序

color = ["red", "yellow", "blue"]
color.sort()
print(color)

结果为：['blue', 'red', 'yellow']

sort和reverse结合一下：

color = ["red", "yellow", "blue"]
color.sort(reverse=True)
print(color)

结果为：['yellow', 'red', 'blue']

b. 使用sorted临时排序

color = ["red", "yellow", "blue"]
print("Here is the original list:",color)
print("Here is the sorted list:", sorted(color))
print("Here is the original list again:",color)

结果为：

Here is the original list: ['red', 'yellow', 'blue']
Here is the sorted list: ['blue', 'red', 'yellow']
Here is the original list again: ['red', 'yellow', 'blue']

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7. reverse反转列表

color = ["red", "yellow", "blue"]
color.reverse()
print(color)

结果为：['blue', 'yellow', 'red']

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8. 复制列表

a. 若直接复制，当原始列表或新列表中的数据发生改变时，新的列表或者原始列表也会发生改变。

color = ["green", "red", "blue"]
color2 = color
color.append("yellow")
print(color2)

结果为：['green', 'red', 'blue', 'yellow']

b. 为了让复制后，原始列表与复制后的列表直接无影响，那么复制操作如下：

color = ["green", "red", "blue"]
color2 = color[:]
color.append("yellow")
print(color2)

结果为：['green', 'red', 'blue']

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9. 列表中的元素可修改，而元组中的元素无法修改

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10. 字典添加键值对

color = {"1": "green", "2" : "red"}
color["3"] = "blue"
print(color)

结果为：{'1': 'green', '2': 'red', '3': 'blue'}

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11. 删除字典中的键值对

color = {"1": "green", "2" : "red"}
del color["2"]
print(color)

结果为：{'1': 'green'}

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12. 遍历字典中的元素

color = {"1": "green", "2":"red"}
for key, value in color.items():
    print("key:", key, end="")
    print("  value:", value)

结果为：

key: 1  value: green
key: 2  value: red

13. 使用input函数输入数据

message = input("Tell me something, and I will repeat it back to you: ")
print(message)

结果为：

Tell me something, and I will repeat it back to you: 123
123