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python Classic exercises

• Exercises 1 ： Output Dictionary key
• • Title Description
  • Question answer
• Exercise 2 ： Output character string with odd position
• • Title Description
  • Question answer
• Conclusion

Exercises 1 ： Output Dictionary key

Title Description

Here is a dictionary a, Such as a = {“honker”: 707, “hacker”: 707, “ker”: 707}, Output Dictionary a Of key, With ’,‘ Connect , Such as ‘honker’,‘hacker’,‘ker’. requirement key In ascending dictionary order
for example ：a = {“honker”: 707, “hacker”: 707, “ker”: 707}, The output ：honker,hacker,ker

Question answer

Use... In the dictionary keys() Method take out all keys , And then use join Method splicing ,sort() Sort by sorting method

a = {
"honker": 707, "hacker": 707, "ker": 707}
keys = a.keys()
k_res = [k for k in keys]
print(','.join(str(k) for k in sorted(k_res)))

Here we need to pay attention to , If you take out the key directly, you will return a dict_keys Type data
Need to traverse the extraction key

a = {
"honker": 707, "hacker": 707, "ker": 707}
keys = a.keys()
print(keys)

The improvement code is as follows ：

a = {
"honker": 707, "hacker": 707, "ker": 707}
keys = a.keys()
k_res = [k for k in keys]
print(','.join(str(k) for k in sorted(k_res)))

The operation results are as follows ：

Exercise 2 ： Output character string with odd position

Title Description

Give you a string a, Output a A string of characters with odd positions in （ The location number is from 1 Start ）.
for example ：a=‘honker’
The output :hne

Question answer

Use the string slice index to get values ( The step size is set to 2 String that can take odd digits )

a = "honker"
print(a[::2])

The operation results are as follows :

Conclusion

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