# 10. String operations

<https://note.nkmk.me/en/python-str-replace-translate-re-sub/>

Here's how to replace strings in Python.

* Replace substrings: `replace()`
  * Specify the maximum count of replacements: `count`
  * Replace multiple different substrings
  * Replace newline character
* Replace multiple different characters: `translate()`
* Replace with regular expression: `re.sub()`, `re.subn()`
  * Replace multiple substrings with the same string
  * Replace using the matched part
  * Get the count of replaced parts
* Replace by position: slice

## Regular Expression

### re.search()

{% tabs %}
{% tab title="Python" %}

```python
for text in df['simplified'][:3]:
    hit = re.search(p, text)
    print(hit)
    print(hit.start(), hit.end())
    print(hit.group())
```

{% endtab %}

{% tab title="output" %}

```
<re.Match object; span=(0, 3), match='特朗普'>
0 3
特朗普
<re.Match object; span=(0, 2), match='美国'>
0 2
美国
<re.Match object; span=(13, 15), match='美国'>
13 15
```

{% endtab %}
{% endtabs %}

### re.finditer()

因為是iterator的關係，可用

{% tabs %}
{% tab title="Python" %}

```python
hits = re.finditer(p, "這個哈哈哈美帝真的北美很討厭")
# print(next(hits))
for h in hits:
    print(h.start(), h.end(), h.group())
```

{% endtab %}

{% tab title="output" %}

```
5 7 美帝
9 11 北美
```

{% endtab %}
{% endtabs %}