﻿ Python: Change a given string to a new string where the first and last chars have been exchanged - w3resource

# Python: Change a given string to a new string where the first and last chars have been exchanged

## Python String: Exercise-10 with Solution

Write a Python program to change a given string to a new string where the first and last chars have been exchanged.

Sample Solution:-

Python Code:

``````def change_sring(str1):
return str1[-1:] + str1[1:-1] + str1[:1]

print(change_sring('abcd'))
print(change_sring('12345'))
```
```

Sample Output:

```dbca
52341
```

Flowchart:

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Python Code Editor:

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## Python: Tips of the Day

Check if a given key already exists in a dictionary:

In is the intended way to test for the existence of a key in a dict.

```d = {"key1": 10, "key2": 23}

if "key1" in d:
print("this will execute")

if "nonexistent key" in d:
print("this will not")
```

If you wanted a default, you can always use dict.get():

```d = dict()

for i in range(100):
key = i % 10
d[key] = d.get(key, 0) + 1
```

and if you wanted to always ensure a default value for any key you can either use dict.setdefault() repeatedly or defaultdict from the collections module, like so:

```from collections import defaultdict

d = defaultdict(int)

for i in range(100):
d[i % 10] += 1
```

but in general, the in keyword is the best way to do it.

Ref: https://bit.ly/2XPMRyz